DefaultHttpHandler 类

定义

public ref class DefaultHttpHandler : System::Web::IHttpAsyncHandler

public class DefaultHttpHandler : System.Web.IHttpAsyncHandler

type DefaultHttpHandler = class
    interface IHttpAsyncHandler
    interface IHttpHandler

Public Class DefaultHttpHandler
Implements IHttpAsyncHandler

继承

Object

DefaultHttpHandler

实现

IHttpAsyncHandler IHttpHandler

示例

下面的代码示例演示如何通过派生自 DefaultHttpHandler 类来实现自定义 HTTP 处理程序。

public class AsyncDefaultHttpHandler : DefaultHttpHandler
{
    private HttpContext _context;

    public override IAsyncResult BeginProcessRequest(
      HttpContext context, AsyncCallback callback, object state)
    {
        AsyncResultSample ar = new AsyncResultSample(callback, state);
        _context = context;

        return ar;
    }

    public override void EndProcessRequest(IAsyncResult result)
    {
        _context.Response.Write("EndProcessRequest called.");
    }

    // This method should not be called asynchronously.
    public override void ProcessRequest(HttpContext context)
    {
        throw new InvalidOperationException(
                  "Asynchronous processing failed.");
    }

    // Enables pooling when set to true
    public override bool IsReusable
    {
        get { return true; }
    }
}

// Tracks state between the begin and end calls.
class AsyncResultSample : IAsyncResult
{
    private AsyncCallback callback = null;
    private Object asyncState;
    private Boolean isCompleted;

    internal AsyncResultSample(AsyncCallback cb, Object state)
    {
        this.callback = cb;
        asyncState = state;
        isCompleted = false;
    }

    public object AsyncState
    {
        get
        {
            return asyncState;
        }
    }

    public bool CompletedSynchronously
    {
        get
        {
            return false;
        }
    }

    public WaitHandle AsyncWaitHandle
    {
        get
        {
            throw new InvalidOperationException(
                      "ASP.NET should not use this property .");
        }
    }

    public bool IsCompleted
    {
        get
        {
            return isCompleted;
        }
    }

    internal void SetCompleted()
    {
        isCompleted = true;
        if (callback != null)
        {
            callback(this);
        }
    }
}

Public Class defaulthttpexampleVB
    Inherits DefaultHttpHandler

    Private _context As HttpContext

    Public Overrides Function BeginProcessRequest _
        (ByVal context As HttpContext, _
         ByVal callback As AsyncCallback, _
         ByVal state As Object) As IAsyncResult

        Dim ar As New AsyncResultSample(callback, state)
        _context = context

        Return (ar)
    End Function

    Public Overrides Sub EndProcessRequest(ByVal result As IAsyncResult)
        _context.Response.Write("EndProcessRequest called.")
    End Sub

    ' This method should not be called asynchronously.
    Public Overrides Sub ProcessRequest(ByVal context As HttpContext)
        Throw New InvalidOperationException _
          ("Asynchronous processing failed.")
    End Sub

    ' Enables pooling when set to true
    Public Overrides ReadOnly Property IsReusable() As Boolean
        Get
            Return True
        End Get
    End Property
End Class

' Tracks state between the begin and end calls.
Class AsyncResultSample
    Implements IAsyncResult
    Private callback As AsyncCallback = Nothing
    Private _asyncState As Object
    Private _isCompleted As Boolean

    Friend Sub New(ByVal cb As AsyncCallback, ByVal state As Object)
        Me.callback = cb
        _asyncState = state
        _isCompleted = False
    End Sub

    Public ReadOnly Property AsyncState() As Object _
      Implements IAsyncResult.AsyncState
        Get
            Return _asyncState
        End Get
    End Property

    Public ReadOnly Property CompletedSynchronously() _
      As Boolean Implements IAsyncResult.CompletedSynchronously
        Get
            Return False
        End Get
    End Property

    Public ReadOnly Property AsyncWaitHandle() _
      As WaitHandle Implements IAsyncResult.AsyncWaitHandle
        Get
            Throw New InvalidOperationException _
              ("ASP.NET should not use this property .")
        End Get
    End Property

    Public ReadOnly Property IsCompleted() _
      As Boolean Implements IAsyncResult.IsCompleted
        Get
            Return IsCompleted
        End Get
    End Property

    Friend Sub SetCompleted()
        _isCompleted = True
        If (callback <> Nothing) Then
            callback(Me)
        End If
    End Sub
End Class

注解

DefaultHttpHandler如果通过 Internet Information Services (IIS) 6.0 配置了两个请求拦截，并且没有显式绑定应用于所请求的扩展，则对象将截获 HTTP 管道中的传入请求。

可以通过 IIS 6.0 中引入的通配符应用程序映射功能设置请求拦截。

类 DefaultHttpHandler 实现 IHttpAsyncHandler 接口以提供异步请求处理。 有关 HTTP 处理程序的一般信息，请参阅 HTTP 处理程序和 HTTP 模块概述。 此外，有关详细信息，请参阅以下内容：

• 关于创建异步 HTTP 处理程序，请参阅 演练：创建异步 HTTP 处理程序。

• 关于注册 HTTP 处理程序，请参阅 如何：注册 HTTP 处理程序。

类可以从 类派生 DefaultHttpHandler ，以提供对请求的自定义处理。 派生自 DefaultHttpHandler 的异步 HTTP 处理程序可以重写 方法， BeginProcessRequest 以更改处理请求的方式。

DefaultHttpHandler不使用 ASP.NET 错误。 使用 IIS 错误或正当 ISAPI 自定义错误机制的现有内容将保持不变。

另请参阅

• 如何：注册 HTTP 处理程序
• 如何：创建异步 HTTP 处理程序