DefaultHttpHandler Class

.NET Framework (current version)

Other Versions

Represents the properties and methods of a default HTTP handler.

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

Inheritance Hierarchy

System.Object
System.Web.DefaultHttpHandler

Syntax

C++

Public Class DefaultHttpHandler
	Implements IHttpAsyncHandler, IHttpHandler

Constructors

	Name	Description
	DefaultHttpHandler()	Initializes a new instance of the DefaultHttpHandler class.

Properties

	Name	Description
	Context	Gets the context that is associated with the current DefaultHttpHandler object.
	ExecuteUrlHeaders	Gets a collection of request headers and request values to transfer along with the request.
	IsReusable	Gets a Boolean value indicating that another request can use the current instance of the DefaultHttpHandler class.

Methods

	Name	Description
	BeginProcessRequest(HttpContext, AsyncCallback, Object)	Initiates an asynchronous call to the HTTP handler.
	EndProcessRequest(IAsyncResult)	Provides an end method for an asynchronous process.
	Equals(Object)	Determines whether the specified object is equal to the current object.(Inherited from Object.)
	Finalize()	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection.(Inherited from Object.)
	GetHashCode()	Serves as the default hash function. (Inherited from Object.)
	GetType()	Gets the Type of the current instance.(Inherited from Object.)
	MemberwiseClone()	Creates a shallow copy of the current Object.(Inherited from Object.)
	OnExecuteUrlPreconditionFailure()	Called when preconditions prevent the DefaultHttpHandler object from processing a request.
	OverrideExecuteUrlPath()	Overrides the target URL for the current request.
	ProcessRequest(HttpContext)	Enables a DefaultHttpHandler object to process of HTTP Web requests.
	ToString()	Returns a string that represents the current object.(Inherited from Object.)

A DefaultHttpHandler object intercepts incoming requests in the HTTP pipeline when both request interception has been configured through Internet Information Services (IIS) 6.0 and no explicit 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 and HTTP Modules Overview. Additionally, for more information see the following:

About creating asynchronous HTTP handlers, see Walkthrough: Creating an Asynchronous HTTP Handler.
About registering HTTP handlers, see How to: Register HTTP Handlers.

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.

Examples

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

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

Version Information

.NET Framework
Available since 2.0

Thread Safety

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