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

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; }  
    }
}

[VisualBasic]
Imports System.Web

Public 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 Property
End 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; }
        }
    }
}

[VisualBasic]
Imports System
Imports System.Web
Imports System.Threading

Namespace 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 Class
End 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>

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VS.Net中的水晶报表的应用 | 在.NET中得到计算机硬件信息的一些功能

2005-05-11 13:33
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