HttpWebRequest.EndGetResponse Method (IAsyncResult)

 

Ends an asynchronous request to an Internet resource.

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

Public Overrides Function EndGetResponse (
	asyncResult As IAsyncResult
) As WebResponse

Parameters

asyncResult
Type: System.IAsyncResult

The pending request for a response.

Return Value

Type: System.Net.WebResponse

A WebResponse that contains the response from the Internet resource.

Exception Condition
ArgumentNullException

asyncResult is null.

InvalidOperationException

This method was called previously using asyncResult.

-or-

The ContentLength property is greater than 0 but the data has not been written to the request stream.

WebException

Abort was previously called.

-or-

An error occurred while processing the request.

ArgumentException

asyncResult was not returned by the current instance from a call to BeginGetResponse.

The EndGetResponse method completes an asynchronous request for an Internet resource that was started by calling the BeginGetResponse method.

System_CAPS_cautionCaution

You must call the Close method to close the stream and release the connection. Failure to do so may cause your application to run out of connections.

System_CAPS_noteNote

This member outputs trace information when you enable network tracing in your application. For more information, see Network Tracing in the .NET Framework.

The following code example uses the EndGetResponse method to end an asynchronous request for an Internet resource.

  Try
    ' Create a new HttpWebrequest object to the desired URL.
    Dim myHttpWebRequest1 As HttpWebRequest = CType(WebRequest.Create("http://www.contoso.com"), HttpWebRequest)

    ' Create an instance of the RequestState and assign the previous myHttpWebRequest1
    ' object to it's request field.  
    Dim myRequestState As New RequestState()
    myRequestState.request = myHttpWebRequest1

    ' Start the Asynchronous request.
    Dim result As IAsyncResult = CType(myHttpWebRequest1.BeginGetResponse(AddressOf RespCallback, myRequestState), IAsyncResult)
    allDone.WaitOne()

    ' Release the HttpWebResponse resource.
    myRequestState.response.Close()
  Catch e As WebException
    Console.WriteLine(ControlChars.Cr + "Exception raised!")
    Console.WriteLine(ControlChars.Cr + "Message:{0}", e.Message)
    Console.WriteLine(ControlChars.Cr + "Status:{0}", e.Status)
    Console.WriteLine("Press any key to continue..........")

  Catch e As Exception
    Console.WriteLine(ControlChars.Cr + "Exception raised!")
    Console.WriteLine("Source :{0} ", e.Source)
    Console.WriteLine("Message : {0}", e.Message)
    Console.WriteLine("Press any key to continue..........")
    Console.Read()
  End Try
End Sub ' Main

Private Shared Sub RespCallback(asynchronousResult As IAsyncResult)
  Try
    ' State of request is asynchronous.
    Dim myRequestState As RequestState = CType(asynchronousResult.AsyncState, RequestState)
    Dim myHttpWebRequest2 As HttpWebRequest = myRequestState.request
    myRequestState.response = CType(myHttpWebRequest2.EndGetResponse(asynchronousResult), HttpWebResponse)
    ' Read the response into a Stream object.
    Dim responseStream As Stream = myRequestState.response.GetResponseStream()
    myRequestState.streamResponse = responseStream
    ' Begin the Reading of the contents of the HTML page and print it to the console.
    Dim asynchronousInputRead As IAsyncResult = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, AddressOf ReadCallBack, myRequestState)
  Catch e As WebException
    Console.WriteLine(ControlChars.Cr + "Exception raised!")
    Console.WriteLine(ControlChars.Cr + "Message:{0}", e.Message)
    Console.WriteLine(ControlChars.Cr + "Status:{0}", e.Status)
  End Try 
End Sub ' RespCallback

Private Shared Sub ReadCallBack(asyncResult As IAsyncResult)
  Try
    Dim myRequestState As RequestState = CType(asyncResult.AsyncState, RequestState)
    Dim responseStream As Stream = myRequestState.streamResponse
    Dim read As Integer = responseStream.EndRead(asyncResult)
    '  Read the HTML page and then print it to the console.
    If read > 0 Then
      myRequestState.requestData.Append(Encoding.ASCII.GetString(myRequestState.BufferRead, 0, read))
      Dim asynchronousResult As IAsyncResult = responseStream.BeginRead(myRequestState.BufferRead, 0, BUFFER_SIZE, AddressOf ReadCallBack, myRequestState)
    Else
      Console.WriteLine(ControlChars.Cr + "The contents of the Html page are : ")
      If myRequestState.requestData.Length > 1 Then
        Dim stringContent As String
        stringContent = myRequestState.requestData.ToString()
        Console.WriteLine(stringContent)
      End If
      Console.WriteLine("Press any key to continue..........")
      Console.ReadLine()
      responseStream.Close()
      allDone.Set()
    End If
  Catch e As WebException
    Console.WriteLine(ControlChars.Cr + "Exception raised!")
    Console.WriteLine(ControlChars.Cr + "Message:{0}", e.Message)
    Console.WriteLine(ControlChars.Cr + "Status:{0}", e.Status)
  End Try 
End Sub ' ReadCallBack

Universal Windows Platform
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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