注册HttpHandler

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在创建了自定义 HttpHandler 后，必须配置 ASP.NET 以便将传入的对特定 URL 的 HTTP 请求映射到处理程序。以下过程描述所需步骤。

注册 HttpHandler

在应用程序的虚拟根目录下的 /bin 目录中编译和部署 HttpHandler 的 .NET 类。
在应用程序的 Web.config 配置文件中注册同步或异步的 HttpHandler。以下示例将所有 HTTP 请求映射到 Myhandler.dll 文件中 MyHandler 程序集的 MyHandler.New 类和 MyHandler.Fin 类。
```
<configuration>    <system.web>        <httpHandlers>            <add verb="*" path="MyHandler.New"                type="MyHandler.New, MyHandlerAssembly" />            <add verb="*" path="*.myNewFileNameExtension"                type="MyHandler.Fin, MyHandlerAssembly" />        </httpHandlers>    <system.web></configuration>
```
<httpHandlers> 配置节中的项具有三个属性，如下表中所示。
属性说明路径路径属性可以包含单个 URL 路径或简单的通配符字符串（例如 *.aspx）。类型指定逗号分隔的类/程序集组合。ASP.NET 首先在应用程序的专用 /bin 目录中搜索程序集 DLL，然后在系统程序集缓存中搜索程序集 DLL。谓词谓词列表可以是逗号分隔的 HTTP 方法列表（例如“GET, PUT, POST”），也可以是开始脚本映射（例如通配符 * [星号]）。
确保将 HttpHandler 文件扩展名注册到 Internet 信息服务 (IIS) 中。

HttpHandler 示例

本节提供下列代码示例：

同步 HttpHandler
异步 HttpHandler
HttpHandler 工厂

同步 HttpHandler

以下代码说明如何在 ASP.NET 应用程序中处理对特定的 MyApp.MyHello URL 的请求。接下来，将显示注册 HttpHandler 所需的配置文件更改。

[C#]using System.Web;public class HelloWorldHandler : IHttpHandler {    public void ProcessRequest(HttpContext context) {        HttpRequest Request = context.Request;        HttpResponse Response = context.Response;        // A file ending in .MyHello need not exist. This handler executes        // whenever a file ending in .MyHello is requested.        Response.Write("<html>");        Response.Write("<body>");        Response.Write("<h1> Hello from Synchronous custom handler. </h1>");        Response.Write("</body>");        Response.Write("</html>");    }    public bool IsReusable {        // To enable pooling, return true here.        // This keeps the handler in memory.        get { return false; }      }}[Visual Basic]Imports System.WebPublic Class HelloWorldHandler    Implements IHttpHandler    Public Sub ProcessRequest(ByVal context As System.Web.HttpContext) Implements System.Web.IHttpHandler.ProcessRequest        Dim request As HttpRequest = context.Request        Dim response As HttpResponse = context.Response        ' A file named ending in .MyHello need not exist. This handler         ' executes whenever a file ending in .MyHello is requested.        response.Write("<html>")        response.Write("<body>")        response.Write("<h1> Hello from Synchronous custom handler. </h1>")        response.Write("</body>")        response.Write("</html>")    End Sub    Public ReadOnly Property IsReusable() As Boolean Implements System.Web.IHttpHandler.IsReusable        Get            Return False        End Get    End PropertyEnd Class

通过在 Web.config 中创建项来注册自定义 HttpHandler，如下所示：

<configuration>    <system.web>        <httpHandlers>           <add verb="*" path="*.MyHello"                 type="HelloWorldHandler,httpruntime" />         </httpHandlers>    </system.web></configuration>

异步 HttpHandler

以下代码说明如何在 ASP.NET 应用程序中注册和处理对特定的 *.MyAsynch URL 的请求。在这种情况下，处理程序启动一个很耗时的进程，在若干时刻向用户发送响应以指示进程。接下来，将显示注册 HttpHandler 所需的配置文件更改。

[C#]using System;using System.Web;using System.Threading;namespace Handlers{    class AsynchHandler : IHttpAsyncHandler    {        private HttpContext _context;        public bool IsReusable        {            get            {                 // To enable pooling, return true here.                 // This keeps the handler in memory.                 return false;            }        }        public IAsyncResult BeginProcessRequest(HttpContext context,            AsyncCallback cb, Object extraData)        {            // Now do something that might take a while.            MyAsynchOperation asynch = new MyAsynchOperation(cb, context);            asynch.KickOffThread();            context.Response.Write("BeginProcessRequest. Just kicked off a Thread.<br>");            context.Response.Flush();            // Signal the application that asynchronous             // processing is being performed.             SomeResult asynchForBegin = new SomeResult();            // Processing is not synchronous.            asynchForBegin.SetSynch(false);            // Processing is not complete.            asynchForBegin.SetCompleted(false);            _context = context;            return new SomeResult();        }        public void EndProcessRequest(IAsyncResult result)        {            _context.Response.Write("EndProcessRequest called.<br>");        }        // This method is required but is not called.        public void ProcessRequest(HttpContext context)        {        }    }//end class    public class SomeResult : IAsyncResult    {    /*    An instance of this class is returned to the application.    This class lets the application know how the BeginEventHandler method         has been handled. The application checks the CompletedSynchronously         method.    */        private bool _blnIsCompleted = false;        private Mutex myMutex = null;        private Object myAsynchStateObject = null;        private bool _blnCompletedSynchronously = false;        public void SetCompleted(bool blnTrueOrFalse)        {            _blnIsCompleted = blnTrueOrFalse;        }        public void SetSynch(bool blnTrueOrFalse)        {            _blnCompletedSynchronously = blnTrueOrFalse;        }        public bool IsCompleted        {            // This is not called by the application.             // However, set it to true.             get { return _blnIsCompleted; }        }        public WaitHandle AsyncWaitHandle        {            // The application does not call this method.                     get { return myMutex; }        }        public Object AsyncState        {              // The application does not call this method because            // null is passed in as the last parameter to             // BeginEventHandler.            get { return myAsynchStateObject; }       }        public bool CompletedSynchronously        {            // The application wants to know if this is synchronous.            // Return true if the Begin method was called synchronously.            get { return _blnCompletedSynchronously; }        }    }}[Visual Basic]Imports SystemImports System.WebImports System.ThreadingNamespace handler    Public Class AsynchHandler        Implements IHttpAsyncHandler        Private _context As HttpContext        Public ReadOnly Property IsReusable() As Boolean Implements System.Web.IHttpAsyncHandler.IsReusable            Get                Return False            End Get        End Property        Public Function BeginProcessRequest(ByVal context As System.Web.HttpContext, ByVal cb As System.AsyncCallback, ByVal extraData As Object) As System.IAsyncResult Implements System.Web.IHttpAsyncHandler.BeginProcessRequest            Dim asynch As New MyAsynchOperation(cb, context)            asynch.KickOffThread()            context.Response.Write("BeginProcessRequest. Just kicked off a Thread.<br>")            context.Response.Flush()            ' Signal the application that asynchronous             ' processing is being performed.             Dim asynchForBegin As New SomeResult()           ' Processing is not synchronous.            asynchForBegin.SetSynch(False)           ' Processing is not complete.            asynchForBegin.SetCompleted(False)            _context = context            Return New SomeResult()        End Function        Public Sub EndProcessRequest(ByVal result As System.IAsyncResult) Implements System.Web.IHttpAsyncHandler.EndProcessRequest            _context.Response.Write("EndProcessRequest called.<br>")        End Sub        Public Sub ProcessRequest(ByVal context As System.Web.HttpContext) Implements System.Web.IHttpAsyncHandler.ProcessRequest            ' Ths is required but is not called.        End Sub    End Class    Class SomeResult        Implements IAsyncResult        Private _blnIsCompleted As Boolean = False        Private myMutex As Mutex = Nothing        Private myAsynchStateObject As Object = Nothing        Private _blnCompletedSynchronously As Boolean = False        Public Sub SetCompleted(ByVal blnTrueOrFalse As Boolean)            _blnIsCompleted = blnTrueOrFalse        End Sub        Public Sub SetSynch(ByVal blnTrueOrFalse As Boolean)            _blnCompletedSynchronously = blnTrueOrFalse        End Sub        Public ReadOnly Property AsyncState() As Object Implements System.IAsyncResult.AsyncState            Get                Return myAsynchStateObject            End Get        End Property        Public ReadOnly Property AsyncWaitHandle() As System.Threading.WaitHandle Implements System.IAsyncResult.AsyncWaitHandle            Get                Return myMutex            End Get        End Property        Public ReadOnly Property CompletedSynchronously() As Boolean Implements System.IAsyncResult.CompletedSynchronously            Get                Return _blnCompletedSynchronously            End Get        End Property        Public ReadOnly Property IsCompleted() As Boolean Implements System.IAsyncResult.IsCompleted            Get                Return _blnIsCompleted            End Get        End Property    End ClassEnd Namespace

通过在 Web.config 中创建项来注册自定义异步 HttpHandler，如下所示：

<configuration>    <system.web>        <httpHandlers>            <add verb="GET,POST" path="*.MyAsynch"                 type="Handlers.AsynchHandler, Handlers" />        </httpHandlers>    </system.web></configuration>