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DefaultHttpHandler Class

Represents the properties and methods of a default HTTP handler.

Namespace: System.Web
Assembly: System.Web (in system.web.dll)

public class DefaultHttpHandler : IHttpAsyncHandler, IHttpHandler
public class DefaultHttpHandler implements IHttpAsyncHandler, IHttpHandler
public class DefaultHttpHandler implements IHttpAsyncHandler, IHttpHandler
Not applicable.

A DefaultHttpHandler object intercepts incoming requests in the HTTP pipeline when both request interception has been configured through Microsoft Internet Information Services (IIS) version 6.0 and no explicit httpHandlers bindings apply to the requested extension.

Request interception can be set up through the wildcard application mapping feature introduced in IIS 6.0. For more information, search the MSDN Library for information about using wildcard application maps to remap a URL.

The DefaultHttpHandler class implements the IHttpAsyncHandler interface to provide asynchronous request processing. For general information about HTTP handlers, see HTTP Handlers. Additionally, for more information:

Classes can derive from the DefaultHttpHandler class to provide customized handling of requests. An asynchronous HTTP handler that is derived from the DefaultHttpHandler could override the BeginProcessRequest method to change how requests are processed.

A DefaultHttpHandler does not use ASP.NET errors. Existing content that uses IIS errors or a propriety ISAPI custom error mechanism would work unchanged.

The following code example demonstrates how to implement a customized HTTP handler by deriving from the DefaultHttpHandler class.

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);
        }
    }

}

System.Object
  System.Web.DefaultHttpHandler

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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