C#_多线程使用初识

学习C#中多线程方法（一）：

WinFrom应用中，创建一个单独的线程执行执行一定的操作，为了向用户现实程序进度，在form中添加progressBar 控件现实进度，通过label显示提示字串。

1. 创建Form，添加progressBar,label, Button 控件

2. 添加引用 system.threading. 这个引用用来创建线程启动操作。

最初的程序为：

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;using System.Threading;namespace ProgressBarTest{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();                    }        private void button1_Click(object sender, EventArgs e)        {            Thread thread = new Thread(new ThreadStart(RunOnTimerThread));            thread.IsBackground = true;            thread.Start();        }        private void RunOnTimerThread()        {            if (progressBar1.Value != 100)            {                progressBar1.Value += 1; //抛出异常            }            if (progressBar2.Value != 100)                progressBar2.Value += 10; //抛出异常            Thread.Sleep(1000);            label1.Text = System.DateTime.Now.ToString(); //抛出异常        }    }}

在编译过程中会返回以下exception: Cross-thread operation not valid: Control 'progressBar1' accessed from a thread other than the thread it was created on.

这里涉及到多线程控制的安全问题，在windows的编程中有这样一个原则，在窗体创建线程之外的任何线程中都不能操作窗体。要解决这个问题，可以调用控件提供的Invoke和BeginInvoke把调用“封送回”窗体创建线程，让程序在窗体创建线程上修改控件属性。下面是修改后的程序：

private void button1_Click(object sender, EventArgs e)        {            Thread thread = new Thread(new ThreadStart(StartSomeWorkFromUIThread));            thread.IsBackground = true;            thread.Start();        }        private void StartSomeWorkFromUIThread()        {            if (this.InvokeRequired)                BeginInvoke(new EventHandler(RunOnTimerThread), null);            else                RunOnTimerThread(this, null);        }        private void RunOnTimerThread(object sender, EventArgs e)        {            if (progressBar1.Value != 100)            {                progressBar1.Value += 1;            }            if (progressBar2.Value != 100)                progressBar2.Value += 10;            Thread.Sleep(1000);            label1.Text = System.DateTime.Now.ToString();        }

参考：http://www.cnblogs.com/jianglai11/articles/1708330.html

http://www.cnblogs.com/net66/archive/2005/08/03/206132.html