程序博客网 > 一组数据的加权平均值

c#多线程与异步开发 （上）

来源：互联网 发布：一组数据的加权平均值 编辑：程序博客网 时间：2024/05/22 06:46

项目中需要一些多线程或异步的知识点，找资料时看到了这篇文章，觉得讲的很不错，转载过来，想要学习的可以看原文，原文链接，感谢原作者提供好文章

引言

本文主要从线程的基础用法，CLR线程池当中工作者线程与I/O线程的开发，并行操作PLINQ等多个方面介绍多线程的开发。 
其中委托的BeginInvoke方法以及回调函数最为常用。 
而 I/O线程可能容易遭到大家的忽略，其实在开发多线程系统，更应该多留意I/O线程的操作。特别是在ASP.NET开发当中，可能更多人只会留意在客户端使用Ajax或者在服务器端使用UpdatePanel。其实合理使用I/O线程在通讯项目或文件下载时，能尽可能地减少IIS的压力。 
并行编程是Framework4.0中极力推广的异步操作方式，更值得更深入地学习。 
希望本篇文章能对各位的学习研究有所帮助，当中有所错漏的地方敬请点评。

一、线程的定义

1. 1 进程、应用程序域与线程的关系

进程（Process）是Windows系统中的一个基本概念，它包含着一个运行程序所需要的资源。进程之间是相对独立的，一个进程无法访问另一个进程的数据（除非利用分布式计算方式），一个进程运行的失败也不会影响其他进程的运行，Windows系统就是利用进程把工作划分为多个独立的区域的。进程可以理解为一个程序的基本边界。

应用程序域（AppDomain）是一个程序运行的逻辑区域，它可以视为一个轻量级的进程，.NET的程序集正是在应用程序域中运行的，一个进程可以包含有多个应用程序域，一个应用程序域也可以包含多个程序集。在一个应用程序域中包含了一个或多个上下文context，使用上下文CLR就能够把某些特殊对象的状态放置在不同容器当中。

线程（Thread）是进程中的基本执行单元，在进程入口执行的第一个线程被视为这个进程的主线程。在.NET应用程序中，都是以Main()方法作为入口的，当调用此方法时系统就会自动创建一个主线程。线程主要是由CPU寄存器、调用栈和线程本地存储器（Thread Local Storage，TLS）组成的。CPU寄存器主要记录当前所执行线程的状态，调用栈主要用于维护线程所调用到的内存与数据，TLS主要用于存放线程的状态信息。

进程、应用程序域、线程的关系如下图，一个进程内可以包括多个应用程序域，也有包括多个线程，线程也可以穿梭于多个应用程序域当中。但在同一个时刻，线程只会处于一个应用程序域内。 
这里写图片描述

1.2 多线程

在单CPU系统的一个单位时间（time slice）内，CPU只能运行单个线程，运行顺序取决于线程的优先级别。如果在单位时间内线程未能完成执行，系统就会把线程的状态信息保存到线程的本地存储器（TLS） 中，以便下次执行时恢复执行。而多线程只是系统带来的一个假像，它在多个单位时间内进行多个线程的切换。因为切换频密而且单位时间非常短暂，所以多线程可被视作同时运行。

适当使用多线程能提高系统的性能，比如：在系统请求大容量的数据时使用多线程，把数据输出工作交给异步线程，使主线程保持其稳定性去处理其他问题。但需要注意一点，因为CPU需要花费不少的时间在线程的切换上，所以过多地使用多线程反而会导致性能的下降。

二、线程的基础知识

2.1 System.Threading.Thread类

System.Threading.Thread是用于控制线程的基础类，通过Thread可以控制当前应用程序域中线程的创建、挂起、停止、销毁。

它包括以下常用公共属性

属性名称说明CurrentContext获取线程正在其中执行的当前上下文。CurrentThread获取当前正在运行的线程。ExecutionContext获取一个 ExecutionContext 对象，该对象包含有关当前线程的各种上下文的信息。IsAlive获取一个值，该值指示当前线程的执行状态。IsBackground获取或设置一个值，该值指示某个线程是否为后台线程。IsThreadPoolThread获取一个值，该值指示线程是否属于托管线程池。ManagedThreadId获取当前托管线程的唯一标识符。Name获取或设置线程的名称。Priority获取或设置一个值，该值指示线程的调度优先级。ThreadState获取一个值，该值包含当前线程的状态。
2.1.1 线程的标识符

ManagedThreadId是确认线程的唯一标识符，程序在大部分情况下都是通过Thread.ManagedThreadId来辨别线程的。而Name是一个可变值，在默认时候，Name为一个空值 Null，开发人员可以通过程序设置线程的名称，但这只是一个辅助功能。

2.1.2 线程的优先级别

.NET为线程设置了Priority属性来定义线程执行的优先级别，里面包含5个选项，其中Normal是默认值。除非系统有特殊要求，否则不应该随便设置线程的优先级别。

成员名称说明Lowest可以将 Thread 安排在具有任何其他优先级的线程之后。BelowNormal可以将 Thread 安排在具有 Normal 优先级的线程之后，在具有 Lowest 优先级的线程之前。Normal默认选择。可以将 Thread 安排在具有 AboveNormal 优先级的线程之后，在具有 BelowNormal 优先级的线程之前。AboveNormal可以将 Thread 安排在具有 Highest 优先级的线程之后，在具有 Normal 优先级的线程之前。Highest可以将 Thread 安排在具有任何其他优先级的线程之前。
2.1.3 线程的状态

通过ThreadState可以检测线程是处于Unstarted、Sleeping、Running 等等状态，它比 IsAlive 属性能提供更多的特定信息。

前面说过，一个应用程序域中可能包括多个上下文，而通过CurrentContext可以获取线程当前的上下文。

CurrentThread是最常用的一个属性，它是用于获取当前运行的线程。

2.1.4 System.Threading.Thread的方法

Thread 中包括了多个方法来控制线程的创建、挂起、停止、销毁，以后来的例子中会经常使用。

方法名称说明Abort()终止本线程。GetDomain()返回当前线程正在其中运行的当前域。GetDomainId()返回当前线程正在其中运行的当前域Id。Interrupt()中断处于 WaitSleepJoin 线程状态的线程。Join()已重载。 阻塞调用线程，直到某个线程终止时为止。Resume()继续运行已挂起的线程。Start()执行本线程。Suspend()挂起当前线程，如果当前线程已属于挂起状态则此不起作用Sleep()把正在运行的线程挂起一段时间。
2.1.5 开发实例

以下这个例子，就是通过Thread显示当前线程信息

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">  static void Main(string[] args)          {              Thread thread = Thread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.CurrentThread</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>              thread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Name</span> = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main Thread"</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>              string threadMessage = string<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Format</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Thread ID:{0}\n    Current AppDomainId:{1}\n    "</span>+                  <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Current ContextId:{2}\n    Thread Name:{3}\n    "</span>+                  <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Thread State:{4}\n    Thread Priority:{5}\n"</span>,                  thread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ManagedThreadId</span>, Thread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.GetDomainID</span>(), Thread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.CurrentContext</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ContextID</span>,                  thread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Name</span>, thread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ThreadState</span>, thread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.Priority</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>             Console<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.WriteLine</span>(threadMessage)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>             Console<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ReadKey</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>         }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li></ul>

运行结果 
这里写图片描述

2.2 System.Threading 命名空间

在System.Threading命名空间内提供多个方法来构建多线程应用程序,其中ThreadPool与Thread是多线程开发中最常用到的，在.NET中专门设定了一个CLR线程池专门用于管理线程的运行，这个CLR线程池正是通过ThreadPool类来管理。而Thread是管理线程的最直接方式，下面几节将详细介绍有关内容。

类说明AutoResetEvent通知正在等待的线程已发生事件。无法继承此类。ExecutionContext管理当前线程的执行上下文。无法继承此类。Interlocked为多个线程共享的变量提供原子操作。Monitor提供同步对对象的访问的机制。Mutex一个同步基元，也可用于进程间同步。Thread创建并控制线程，设置其优先级并获取其状态。ThreadAbortException在对 Abort 方法进行调用时引发的异常。无法继承此类。ThreadPool提供一个线程池，该线程池可用于发送工作项、处理异步 I/O、代表其他线程等待以及处理计时器。Timeout包含用于指定无限长的时间的常数。无法继承此类。Timer提供以指定的时间间隔执行方法的机制。无法继承此类。WaitHandle封装等待对共享资源的独占访问的操作系统特定的对象。

在System.Threading中的包含了下表中的多个常用委托，其中ThreadStart、ParameterizedThreadStart是最常用到的委托。 
由ThreadStart生成的线程是最直接的方式，但由ThreadStart所生成并不受线程池管理。 
而ParameterizedThreadStart是为异步触发带参数的方法而设的，在下一节将为大家逐一细说。

委托说明ContextCallback表示要在新上下文中调用的方法。ParameterizedThreadStart表示在 Thread 上执行的方法。ThreadExceptionEventHandler表示将要处理 Application 的 ThreadException 事件的方法。ThreadStart表示在 Thread 上执行的方法。TimerCallback表示处理来自 Timer 的调用的方法。WaitCallback表示线程池线程要执行的回调方法。WaitOrTimerCallback表示当 WaitHandle 超时或终止时要调用的方法。
2.3 线程的管理方式

通过ThreadStart来创建一个新线程是最直接的方法，但这样创建出来的线程比较难管理，如果创建过多的线程反而会让系统的性能下载。有见及此，.NET为线程管理专门设置了一个CLR线程池，使用CLR线程池系统可以更合理地管理线程的使用。所有请求的服务都能运行于线程池中，当运行结束时线程便会回归到线程池。通过设置，能控制线程池的最大线程数量，在请求超出线程最大值时，线程池能按照操作的优先级别来执行，让部分操作处于等待状态，待有线程回归时再执行操作。

基础知识就为大家介绍到这里，下面将详细介绍多线程的开发。

三、以ThreadStart方式实现多线程

3.1 使用ThreadStart委托

这里先以一个例子体现一下多线程带来的好处，首先在Message类中建立一个方法ShowMessage()，里面显示了当前运行线程的Id，并使用Thread.Sleep（int ) 方法模拟部分工作。在main()中通过ThreadStart委托绑定Message对象的ShowMessage（）方法，然后通过Thread.Start（）执行异步方法。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Message      {          <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">ShowMessage</span>()          {              <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> message = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async threadId is :{0}"</span>,                                              Thread.CurrentThread.ManagedThreadId);              Console.WriteLine(message);              <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> n = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; n < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>; n++)              {                  Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>);                     Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"The number is:"</span> + n.ToString());               }          }      }      class Program      {          <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>[] args)          {              Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main threadId is:"</span>+                                Thread.CurrentThread.ManagedThreadId);              Message message=<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Message();              Thread thread = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadStart(message.ShowMessage));              thread.Start();              Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Do something ..........!"</span>);              Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main thread working is complete!"</span>);          }      }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li></ul>

请注意运行结果，在调用Thread.Start()方法后，系统以异步方式运行Message.ShowMessage()，而主线程的操作是继续执行的，在Message.ShowMessage()完成前，主线程已完成所有的操作。 
这里写图片描述

3.2 使用ParameterizedThreadStart委托

ParameterizedThreadStart委托与ThreadStart委托非常相似，但ParameterizedThreadStart委托是面向带参数方法的。注意ParameterizedThreadStart 对应方法的参数为object，此参数可以为一个值对象，也可以为一个自定义对象。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Person    {        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> Name        {            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>;            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>;        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> Age        {            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>;            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">set</span>;        }    }    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Message    {        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">ShowMessage</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">object</span> person)        {            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (person != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>)            {                Person _person = (Person)person;                <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> message = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"\n{0}'s age is {1}!\nAsync threadId is:{2}"</span>,                    _person.Name,_person.Age,Thread.CurrentThread.ManagedThreadId);                Console.WriteLine(message);            }            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> n = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; n < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>; n++)            {                Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>);                   Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"The number is:"</span> + n.ToString());             }        }    }    class Program    {        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>[] args)        {                 Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main threadId is:"</span>+Thread.CurrentThread.ManagedThreadId);            Message message=<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Message();            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//绑定带参数的异步方法</span>            Thread thread = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ParameterizedThreadStart(message.ShowMessage));            Person person = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Person();            person.Name = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Jack"</span>;            person.Age = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">21</span>;            thread.Start(person);  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//启动异步线程 </span>            Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Do something ..........!"</span>);            Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main thread working is complete!"</span>);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li></ul>

运行结果： 
这里写图片描述

3.3 前台线程与后台线程

注意以上两个例子都没有使用Console.ReadKey（）,但系统依然会等待异步线程完成后才会结束。这是因为使用Thread.Start()启动的线程默认为前台线程，而系统必须等待所有前台线程运行结束后，应用程序域才会自动卸载。

在第二节曾经介绍过线程Thread有一个属性IsBackground，通过把此属性设置为true，就可以把线程设置为后台线程！这时应用程序域将在主线程完成时就被卸载，而不会等待异步线程的运行。

3.4 挂起线程

为了等待其他后台线程完成后再结束主线程，就可以使用Thread.Sleep()方法。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Message    {        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">ShowMessage</span>()        {            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> message = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"\nAsync threadId is:{0}"</span>,                                           Thread.CurrentThread.ManagedThreadId);            Console.WriteLine(message);            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> n = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; n < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>; n++)            {                Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>);                Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"The number is:"</span> + n.ToString());            }        }    }    class Program    {        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>[] args)        {                 Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main threadId is:"</span>+                              Thread.CurrentThread.ManagedThreadId);            Message message=<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Message();            Thread thread = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadStart(message.ShowMessage));            thread.IsBackground = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>;            thread.Start();            Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Do something ..........!"</span>);            Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main thread working is complete!"</span>);            Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main thread sleep!"</span>);            Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5000</span>);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li></ul>

运行结果如下，此时应用程序域将在主线程运行5秒后自动结束 
这里写图片描述

但系统无法预知异步线程需要运行的时间，所以用通过Thread.Sleep（int）阻塞主线程并不是一个好的解决方法。有见及此，.NET专门为等待异步线程完成开发了另一个方法thread.Join()。把上面例子中的最后一行Thread.Sleep（5000）修改为 thread.Join() 就能保证主线程在异步线程thread运行结束后才会终止。

3.5 Suspend 与 Resume （慎用）

Thread.Suspend（）与 Thread.Resume（）是在Framework1.0 就已经存在的老方法了，它们分别可以挂起、恢复线程。但在Framework2.0中就已经明确排斥这两个方法。这是因为一旦某个线程占用了已有的资源，再使用Suspend（）使线程长期处于挂起状态，当在其他线程调用这些资源的时候就会引起死锁！所以在没有必要的情况下应该避免使用这两个方法。

3.6 终止线程

若想终止正在运行的线程，可以使用Abort（）方法。在使用Abort（）的时候，将引发一个特殊异常 ThreadAbortException 。 
若想在线程终止前恢复线程的执行，可以在捕获异常后 ,在catch（ThreadAbortException ex）{…} 中调用Thread.ResetAbort（）取消终止。 
而使用Thread.Join（）可以保证应用程序域等待异步线程结束后才终止运行。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>[] args)         {             Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main threadId is:"</span> +                               Thread.CurrentThread.ManagedThreadId);             Thread thread = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Thread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> ThreadStart(AsyncThread));             thread.IsBackground = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>;             thread.Start();             thread.Join();         }              <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//以异步方式调用</span>         <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> AsyncThread()         {             <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span>             {                 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> message = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"\nAsync threadId is:{0}"</span>,                    Thread.CurrentThread.ManagedThreadId);                 Console.WriteLine(message);                 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> n = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; n < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>; n++)                 {                     <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//当n等于4时，终止线程</span>                     <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (n >= <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">4</span>)                     {                         Thread.CurrentThread.Abort(n);                     }                     Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">300</span>);                     Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"The number is:"</span> + n.ToString());                 }             }             <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (ThreadAbortException ex)             {                 <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//输出终止线程时n的值</span>                 <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (ex.ExceptionState != <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">null</span>)                     Console.WriteLine(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Thread abort when the number is: {0}!"</span>,                                                       ex.ExceptionState.ToString()));                 <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//取消终止，继续执行线程</span>                 Thread.ResetAbort();                 Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Thread ResetAbort!"</span>);             }             <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//线程结束</span>             Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Thread Close!"</span>);         }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li></ul>

运行结果如下 
这里写图片描述

四、CLR线程池的工作者线程

4.1 关于CLR线程池

使用ThreadStart与ParameterizedThreadStart建立新线程非常简单，但通过此方法建立的线程难于管理，若建立过多的线程反而会影响系统的性能。 
有见及此，.NET引入CLR线程池这个概念。CLR线程池并不会在CLR初始化的时候立刻建立线程，而是在应用程序要创建线程来执行任务时，线程池才初始化一个线程。线程的初始化与其他的线程一样。在完成任务以后，该线程不会自行销毁，而是以挂起的状态返回到线程池。直到应用程序再次向线程池发出请求时，线程池里挂起的线程就会再度激活执行任务。这样既节省了建立线程所造成的性能损耗，也可以让多个任务反复重用同一线程，从而在应用程序生存期内节约大量开销。

注意：通过CLR线程池所建立的线程总是默认为后台线程，优先级数为ThreadPriority.Normal。

4.2 工作者线程与I/O线程

CLR线程池分为工作者线程（workerThreads）与I/O线程 (completionPortThreads) 两种，工作者线程是主要用作管理CLR内部对象的运作，I/O（Input/Output) 线程顾名思义是用于与外部系统交换信息，IO线程的细节将在下一节详细说明。

通过ThreadPool.GetMax（out int workerThreads,out int completionPortThreads )和 ThreadPool.SetMax( int workerThreads, int completionPortThreads)两个方法可以分别读取和设置CLR线程池中工作者线程与I/O线程的最大线程数。在Framework2.0中最大线程默认为25*CPU数，在Framewok3.0、4.0中最大线程数默认为250*CPU数，在近年 I3,I5,I7 CPU出现后，线程池的最大值一般默认为1000、2000。 
若想测试线程池中有多少的线程正在投入使用，可以通过ThreadPool.GetAvailableThreads( out int workerThreads,out int completionPortThreads ) 方法。

使用CLR线程池的工作者线程一般有两种方式，一是直接通过 ThreadPool.QueueUserWorkItem() 方法，二是通过委托，下面将逐一细说。

4.3 通过QueueUserWorkItem启动工作者线程

ThreadPool线程池中包含有两个静态方法可以直接启动工作者线程： 
一为 ThreadPool.QueueUserWorkItem(WaitCallback) 
二为 ThreadPool.QueueUserWorkItem(WaitCallback,Object)

先把WaitCallback委托指向一个带有Object参数的无返回值方法，再使用 ThreadPool.QueueUserWorkItem(WaitCallback) 就可以异步启动此方法，此时异步方法的参数被视为null 。

<code class="hljs vala has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Program</span>    {</span>        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>[] args)        {            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//把CLR线程池的最大值设置为1000</span>            ThreadPool.SetMaxThreads(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1000</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1000</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//显示主线程启动时线程池信息</span>            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Start"</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//启动工作者线程</span>            ThreadPool.QueueUserWorkItem(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> WaitCallback(AsyncCallback));            Console.ReadKey();        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> AsyncCallback(object state)        {            Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">200</span>);            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"AsyncCallback"</span>);            Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async thread do work!"</span>);        }        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//显示线程现状</span>        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> ThreadMessage(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> data)        {            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> message = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"{0}\n  CurrentThreadId is {1}"</span>,                 data, Thread.CurrentThread.ManagedThreadId);            Console.WriteLine(message);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li></ul>

运行结果 
这里写图片描述

使用 ThreadPool.QueueUserWorkItem(WaitCallback,Object) 方法可以把object对象作为参数传送到回调函数中。 
下面例子中就是把一个string对象作为参数发送到回调函数当中。

<code class="hljs vala has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">Program</span>    {</span>        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>[] args)        {            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//把线程池的最大值设置为1000</span>            ThreadPool.SetMaxThreads(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1000</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1000</span>);            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Start"</span>);            ThreadPool.QueueUserWorkItem(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> WaitCallback(AsyncCallback),<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Hello Elva"</span>);            Console.ReadKey();        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> AsyncCallback(object state)        {            Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">200</span>);            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"AsyncCallback"</span>);            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> data = (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>)state;            Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async thread do work!\n"</span>+data);        }        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//显示线程现状</span>        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> ThreadMessage(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> data)        {            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> message = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"{0}\n  CurrentThreadId is {1}"</span>,                 data, Thread.CurrentThread.ManagedThreadId);            Console.WriteLine(message);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li></ul>

运行结果 
这里写图片描述

通过ThreadPool.QueueUserWorkItem启动工作者线程虽然是方便，但WaitCallback委托指向的必须是一个带有Object参数的无返回值方法，这无疑是一种限制。若方法需要有返回值，或者带有多个参数，这将多费周折。有见及此，.NET提供了另一种方式去建立工作者线程，那就是委托。

4.4 委托类　　　　　　　

使用CLR线程池中的工作者线程，最灵活最常用的方式就是使用委托的异步方法，在此先简单介绍一下委托类。

当定义委托后，.NET就会自动创建一个代表该委托的类，下面可以用反射方式显示委托类的方法成员

<code class="hljs haskell has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-class" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Program</span>    {        delegate void <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">MyDelegate</span><span class="hljs-container" style="box-sizing: border-box;">()</span>;        static void <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Main</span><span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">string</span>[] <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">args</span>)</span>        {            <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">MyDelegate</span> delegate1 = new <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">MyDelegate</span><span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">AsyncThread</span>)</span>;            //显示委托类的几个方法成员                 var methods=delegate1.<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">GetType</span><span class="hljs-container" style="box-sizing: border-box;">()</span>.<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">GetMethods</span><span class="hljs-container" style="box-sizing: border-box;">()</span>;            if <span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">methods</span> != <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">null</span>)</span>                foreach <span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">MethodInfo</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">info</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">in</span> <span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">methods</span>)</span>                    <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Console</span>.<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">WriteLine</span><span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box; color: rgb(102, 0, 102);">info</span>.<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Name</span>)</span>;            <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Console</span>.<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">ReadKey</span><span class="hljs-container" style="box-sizing: border-box;">()</span>;         }     }</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li></ul>

委托类包括以下几个重要方法 
这里写图片描述

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> MyDelegate:MulticastDelegate    {        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-title" style="box-sizing: border-box;">MyDelegate</span>(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">object</span> target, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> methodPtr);        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//调用委托方法</span>        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">virtual</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">Invoke</span>();        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//异步委托</span>        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">virtual</span> IAsyncResult <span class="hljs-title" style="box-sizing: border-box;">BeginInvoke</span>(AsyncCallback callback,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">object</span> state);        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">virtual</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">EndInvoke</span>(IAsyncResult result);    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

当调用Invoke（）方法时，对应此委托的所有方法都会被执行。而BeginInvoke与EndInvoke则支持委托方法的异步调用，由BeginInvoke启动的线程都属于CLR线程池中的工作者线程，在下面将详细说明。

4.5 利用BeginInvoke与EndInvoke完成异步委托方法

首先建立一个委托对象，通过IAsyncResult BeginInvoke(string name,AsyncCallback callback,object state) 异步调用委托方法，BeginInvoke 方法除最后的两个参数外，其它参数都是与方法参数相对应的。通过 BeginInvoke 方法将返回一个实现了 System.IAsyncResult 接口的对象，之后就可以利用EndInvoke（IAsyncResult ) 方法就可以结束异步操作，获取委托的运行结果。

<code class="hljs d has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Program    {        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">delegate</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> MyDelegate(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name);        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>[] args)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main Thread"</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//建立委托</span>            MyDelegate myDelegate = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyDelegate(Hello);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//异步调用委托，获取计算结果</span>            IAsyncResult result=myDelegate.BeginInvoke(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Leslie"</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//完成主线程其他工作</span>            .............             <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//等待异步方法完成，调用EndInvoke(IAsyncResult)获取运行结果</span>            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data=myDelegate.EndInvoke(result);            Console.WriteLine(data);            Console.ReadKey();        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> Hello(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async Thread"</span>);            Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2000</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//虚拟异步工作</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Hello "</span> + name;        }        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//显示当前线程</span>        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> ThreadMessage(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data)        {            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> message = <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"{0}\n  ThreadId is:{1}"</span>,                   data,Thread.CurrentThread.ManagedThreadId);            Console.WriteLine(message);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li></ul>

运行结果 
这里写图片描述

4.6 善用IAsyncResult

在以上例子中可以看见，如果在使用myDelegate.BeginInvoke后立即调用myDelegate.EndInvoke，那在异步线程未完成工作以前主线程将处于阻塞状态，等到异步线程结束获取计算结果后，主线程才能继续工作，这明显无法展示出多线程的优势。此时可以好好利用IAsyncResult 提高主线程的工作性能，IAsyncResult有以下成员：

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">interface</span> IAsyncResult{    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">object</span> AsyncState {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>;}            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//获取用户定义的对象，它限定或包含关于异步操作的信息。</span>    WailHandle AsyncWaitHandle {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>;}   <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//获取用于等待异步操作完成的 WaitHandle。</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">bool</span> CompletedSynchronously {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>;}  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//获取异步操作是否同步完成的指示。</span>    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">bool</span> IsCompleted {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">get</span>;}             <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//获取异步操作是否已完成的指示。</span>}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>

通过轮询方式，使用IsCompleted属性判断异步操作是否完成，这样在异步操作未完成前就可以让主线程执行另外的工作。

<code class="hljs d has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Program    {        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">delegate</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> MyDelegate(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name);        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>[] args)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main Thread"</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//建立委托</span>            MyDelegate myDelegate = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyDelegate(Hello);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//异步调用委托，获取计算结果</span>            IAsyncResult result=myDelegate.BeginInvoke(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Leslie"</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//在异步线程未完成前执行其他工作</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (!result.IsCompleted)            {                Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">200</span>);      <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//虚拟操作</span>                Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main thead do work!"</span>);            }            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data=myDelegate.EndInvoke(result);            Console.WriteLine(data);            Console.ReadKey();        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> Hello(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async Thread"</span>);            Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2000</span>);            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Hello "</span> + name;        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> ThreadMessage(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data)        {            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> message = <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"{0}\n  ThreadId is:{1}"</span>,                   data,Thread.CurrentThread.ManagedThreadId);            Console.WriteLine(message);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li></ul>

运行结果： 
这里写图片描述

除此以外，也可以使用WailHandle完成同样的工作，WaitHandle里面包含有一个方法WaitOne（int timeout），它可以判断委托是否完成工作，在工作未完成前主线程可以继续其他工作。运行下面代码可得到与使用 IAsyncResult.IsCompleted 同样的结果，而且更简单方便 。

<code class="hljs d has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">namespace Test{    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Program    {        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">delegate</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> MyDelegate(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name);        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>[] args)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main Thread"</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//建立委托</span>            MyDelegate myDelegate = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyDelegate(Hello);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//异步调用委托，获取计算结果</span>            IAsyncResult result=myDelegate.BeginInvoke(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Leslie"</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>);            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (!result.AsyncWaitHandle.WaitOne(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">200</span>))            {                Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main thead do work!"</span>);            }            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data=myDelegate.EndInvoke(result);            Console.WriteLine(data);            Console.ReadKey();        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> Hello(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async Thread"</span>);            Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2000</span>);            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Hello "</span> + name;        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> ThreadMessage(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data)        {            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> message = <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"{0}\n  ThreadId is:{1}"</span>,                   data,Thread.CurrentThread.ManagedThreadId);            Console.WriteLine(message);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li></ul>

当要监视多个运行对象的时候，使用IAsyncResult.WaitHandle.WaitOne可就派不上用场了。 
幸好.NET为WaitHandle准备了另外两个静态方法：WaitAny（waitHandle[], int）与WaitAll (waitHandle[] , int)。 
其中WaitAll在等待所有waitHandle完成后再返回一个bool值。 
而WaitAny是等待其中一个waitHandle完成后就返回一个int，这个int是代表已完成waitHandle在waitHandle[]中的数组索引。 
下面就是使用WaitAll的例子，运行结果与使用 IAsyncResult.IsCompleted 相同。

<code class="hljs d has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Program    {        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">delegate</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> MyDelegate(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name);        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>[] args)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main Thread"</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//建立委托</span>            MyDelegate myDelegate = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyDelegate(Hello);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//异步调用委托，获取计算结果</span>            IAsyncResult result=myDelegate.BeginInvoke(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Leslie"</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>, <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//此处可加入多个检测对象</span>            WaitHandle[] waitHandleList = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> WaitHandle[] { result.AsyncWaitHandle,........ };            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (!WaitHandle.WaitAll(waitHandleList,<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">200</span>))            {                Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main thead do work!"</span>);            }            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data=myDelegate.EndInvoke(result);            Console.WriteLine(data);            Console.ReadKey();        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> Hello(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async Thread"</span>);            Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2000</span>);            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Hello "</span> + name;        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> ThreadMessage(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data)        {            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> message = <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"{0}\n  ThreadId is:{1}"</span>,                   data,Thread.CurrentThread.ManagedThreadId);            Console.WriteLine(message);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li></ul>
4.7 回调函数

使用轮询方式来检测异步方法的状态非常麻烦，而且效率不高，有见及此，.NET为 IAsyncResult BeginInvoke（AsyncCallback , object）准备了一个回调函数。使用 AsyncCallback 就可以绑定一个方法作为回调函数，回调函数必须是带参数 IAsyncResult 且无返回值的方法： void AsycnCallbackMethod(IAsyncResult result) 。在BeginInvoke方法完成后，系统就会调用AsyncCallback所绑定的回调函数,最后回调函数中调用 XXX EndInvoke（IAsyncResult result) 就可以结束异步方法，它的返回值类型与委托的返回值一致。

<code class="hljs d has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Program    {        <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">delegate</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> MyDelegate(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name);        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>[] args)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main Thread"</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//建立委托</span>            MyDelegate myDelegate = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyDelegate(Hello);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//异步调用委托，获取计算结果</span>            myDelegate.BeginInvoke(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Leslie"</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> AsyncCallback(Completed), <span class="hljs-literal" style="color: rgb(0, 102, 102); box-sizing: border-box;">null</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//在启动异步线程后，主线程可以继续工作而不需要等待</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> n = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; n < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6</span>; n++)                Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"  Main thread do work!"</span>);            Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">""</span>);            Console.ReadKey();        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> Hello(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> name)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async Thread"</span>);            Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2000</span>);             \\模拟异步操作            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"\nHello "</span> + name;        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Completed(IAsyncResult result)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async Completed"</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//获取委托对象，调用EndInvoke方法获取运行结果</span>            AsyncResult _result = (AsyncResult)result;            MyDelegate myDelegate = (MyDelegate)_result.AsyncDelegate;            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data = myDelegate.EndInvoke(_result);            Console.WriteLine(data);        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> ThreadMessage(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> data)        {            <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span> message = <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"{0}\n  ThreadId is:{1}"</span>,                   data, Thread.CurrentThread.ManagedThreadId);            Console.WriteLine(message);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li></ul>

可以看到，主线在调用BeginInvoke方法可以继续执行其他命令，而无需再等待了，这无疑比使用轮询方式判断异步方法是否完成更有优势。 
在异步方法执行完成后将会调用AsyncCallback所绑定的回调函数，注意一点，回调函数依然是在异步线程中执行，这样就不会影响主线程的运行，这也使用回调函数最值得青昧的地方。 
在回调函数中有一个既定的参数IAsyncResult,把IAsyncResult强制转换为AsyncResult后，就可以通过 AsyncResult.AsyncDelegate 获取原委托，再使用EndInvoke方法获取计算结果。 
运行结果如下： 
这里写图片描述

如果想为回调函数传送一些外部信息，就可以利用BeginInvoke(AsyncCallback,object)的最后一个参数object,它允许外部向回调函数输入任何类型的参数。只需要在回调函数中利用 AsyncResult.AsyncState 就可以获取object对象。

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">class Program    {        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> Person        {            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> Name;            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> Age;        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">delegate</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> MyDelegate(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> name);        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Main(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>[] args)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Main Thread"</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//建立委托</span>            MyDelegate myDelegate = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MyDelegate(Hello);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//建立Person对象</span>            Person person = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> Person();            person.Name = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Elva"</span>;            person.Age = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">27</span>;            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//异步调用委托，输入参数对象person, 获取计算结果</span>            myDelegate.BeginInvoke(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Leslie"</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> AsyncCallback(Completed), person);                        <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//在启动异步线程后，主线程可以继续工作而不需要等待</span>            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> n = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; n < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">6</span>; n++)                Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"  Main thread do work!"</span>);            Console.WriteLine(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">""</span>);            Console.ReadKey();        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> Hello(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> name)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async Thread"</span>);            Thread.Sleep(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">2000</span>);            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"\nHello "</span> + name;        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> Completed(IAsyncResult result)        {            ThreadMessage(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Async Completed"</span>);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//获取委托对象，调用EndInvoke方法获取运行结果</span>            AsyncResult _result = (AsyncResult)result;            MyDelegate myDelegate = (MyDelegate)_result.AsyncDelegate;            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> data = myDelegate.EndInvoke(_result);            <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//获取Person对象</span>            Person person = (Person)result.AsyncState;            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> message = person.Name + <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"'s age is "</span> + person.Age.ToString();            Console.WriteLine(data+<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"\n"</span>+message);        }        <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> ThreadMessage(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> data)        {            <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span> message = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">string</span>.Format(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"{0}\n  ThreadId is:{1}"</span>,                   data, Thread.CurrentThread.ManagedThreadId);            Console.WriteLine(message);        }    }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li></ul>

运行结果: 
这里写图片描述

0 0
一组数据的加权平均值 一组数据的加权平均值
原创粉丝点击
热门IT博客
ubuntu 关闭apache2ubuntu 关闭apache2
jackson java转jsonjackson java转json
北航软件学院教务
plu直播软件
数据分析方法回归分析
java生成二维码图片
ubuntu下格式化u盘
java get set方法例子
linux怎么查看log文件
课程录制软件
淘宝坑位产值计算公式
男双肩包推荐 知乎
网络货币投资产品
重庆时时彩助赢软件
思启网络
linux如何关闭echo
java防止xss攻击代码
互联网电商公关 知乎
linux下如何同步时钟
linux没有iptables文件
热门问题 老师的惩罚 人脸识别 我在镇武司摸鱼那些年 重生之率土为王 我在大康的咸鱼生活 盘龙之生命进化 天生仙种 凡人之先天五行 春回大明朝 姑娘不必设防，我是瞎子 清河学区房 清河园小区 清河房子 清河中学 清河堂 清河 楼盘 清河小营 清河公园 清河嘉园 清河在哪里 清河租房网 清河在哪 清河酒 清河旅行社 清河房源 清河站 清河火车站 清河学前班 清河信息网 清河 房价 清河高中 清河自流平 清河出租 清河房产网 清河房地产 清河卖房 清河郡 清河驾校 清河书法 清河派出所 清河拆迁 清河合租房 清河男科 清河 买房 清河菜市场 学而思清河 清河妇幼 学而思 清河 清河花苑 清河二中 清河 学前班

程序博客网，程序员的互联网技术博客家园。csdn论坛精品 msdn技术资料都在这里