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WebRequest.BeginGetResponse Method

When overridden in a descendant class, begins an asynchronous request for an Internet resource.

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

public virtual IAsyncResult BeginGetResponse (
	AsyncCallback callback,
	Object state
)
public IAsyncResult BeginGetResponse (
	AsyncCallback callback, 
	Object state
)
public function BeginGetResponse (
	callback : AsyncCallback, 
	state : Object
) : IAsyncResult

Parameters

callback

The AsyncCallback delegate.

state

An object containing state information for this asynchronous request.

Return Value

An IAsyncResult that references the asynchronous request.

Exception typeCondition

NotImplementedException

Any attempt is made to access the method, when the method is not overridden in a descendant class.

The BeginGetResponse method starts an asynchronous request for a response. The callback method that implements the AsyncCallback delegate uses the EndGetResponse method to return the WebResponse from the Internet resource.

NoteNote

The WebRequest class is an abstract class. The actual behavior of WebRequest instances at run time is determined by the descendant class returned by the System.Net.WebRequest.Create method. For more information about default values and exceptions, see the documentation for the descendant classes, such as HttpWebRequest and FileWebRequest.

NoteNote

If a WebException is thrown, use the Response and Status properties of the exception to determine the response from the server.

The following example uses BeginGetResponse to asynchronously request the target resource. When the resource has been obtained, the specified callback method will be executed.


using System;
using System.Net;
using System.IO;
using System.Text;
using System.Threading;



public class RequestState
{
  // This class stores the state of the request.
  const int BUFFER_SIZE = 1024;
  public StringBuilder requestData;
  public byte[] bufferRead;
  public WebRequest request;
  public WebResponse response;
  public Stream responseStream;
  public RequestState()
  {
    bufferRead = new byte[BUFFER_SIZE];
    requestData = new StringBuilder("");
    request = null;
    responseStream = null;
  }
}
class WebRequest_BeginGetResponse
{
  public static ManualResetEvent allDone= new ManualResetEvent(false);
  const int BUFFER_SIZE = 1024;
  static void Main()
  {
    try
    {
      // Create a new webrequest to the mentioned URL.   
      WebRequest myWebRequest= WebRequest.Create("http://www.contoso.com");
      
      // Please, set the proxy to a correct value. 
      WebProxy proxy=new WebProxy("myproxy:80");

      proxy.Credentials=new NetworkCredential("srikun","simrin123");
      myWebRequest.Proxy=proxy;
      // Create a new instance of the RequestState.
      RequestState myRequestState = new RequestState();
      // The 'WebRequest' object is associated to the 'RequestState' object.
      myRequestState.request = myWebRequest;
      // Start the Asynchronous call for response.
      IAsyncResult asyncResult=(IAsyncResult) myWebRequest.BeginGetResponse(new AsyncCallback(RespCallback),myRequestState);
      allDone.WaitOne();
      // Release the WebResponse resource.
      myRequestState.response.Close();
      Console.Read();
    }
    catch(WebException e)
    {
      Console.WriteLine("WebException raised!");
      Console.WriteLine("\n{0}",e.Message);
      Console.WriteLine("\n{0}",e.Status);
    } 
    catch(Exception e)
    {
      Console.WriteLine("Exception raised!");
      Console.WriteLine("Source : " + e.Source);
      Console.WriteLine("Message : " + e.Message);
    }
  }
  private static void RespCallback(IAsyncResult asynchronousResult)
  {  
    try
    {
      // Set the State of request to asynchronous.
      RequestState myRequestState=(RequestState) asynchronousResult.AsyncState;
      WebRequest  myWebRequest1=myRequestState.request;
      // End the Asynchronous response.
      myRequestState.response =  myWebRequest1.EndGetResponse(asynchronousResult);
      // Read the response into a 'Stream' object.
      Stream responseStream = myRequestState.response.GetResponseStream();
      myRequestState.responseStream=responseStream;
      // Begin the reading of the contents of the HTML page and print it to the console.
      IAsyncResult asynchronousResultRead = responseStream.BeginRead(myRequestState.bufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
    
    }
    catch(WebException e)
    {
      Console.WriteLine("WebException raised!");
      Console.WriteLine("\n{0}",e.Message);
      Console.WriteLine("\n{0}",e.Status);
    } 
    catch(Exception e)
    {
      Console.WriteLine("Exception raised!");
      Console.WriteLine("Source : " + e.Source);
      Console.WriteLine("Message : " + e.Message);
    }
  }
  private static  void ReadCallBack(IAsyncResult asyncResult)
  {
    try
    {
      // Result state is set to AsyncState.
      RequestState myRequestState = (RequestState)asyncResult.AsyncState;
      Stream responseStream = myRequestState.responseStream;
      int read = responseStream.EndRead( asyncResult );
      // Read the contents of the HTML page and then print to the console.
      if (read > 0)
      {
        myRequestState.requestData.Append(Encoding.ASCII.GetString(myRequestState.bufferRead, 0, read));
        IAsyncResult asynchronousResult = responseStream.BeginRead( myRequestState.bufferRead, 0, BUFFER_SIZE, new AsyncCallback(ReadCallBack), myRequestState);
      }
      else
      {
        Console.WriteLine("\nThe HTML page Contents are:  ");
        if(myRequestState.requestData.Length>1)
        {
          string sringContent;
          sringContent = myRequestState.requestData.ToString();
          Console.WriteLine(sringContent);
        }
        Console.WriteLine("\nPress 'Enter' key to continue........");
        responseStream.Close();
        allDone.Set();
      }
    }
    catch(WebException e)
    {
      Console.WriteLine("WebException raised!");
      Console.WriteLine("\n{0}",e.Message);
      Console.WriteLine("\n{0}",e.Status);
    } 
    catch(Exception e)
    {
      Console.WriteLine("Exception raised!");
      Console.WriteLine("Source : {0}" , e.Source);
      Console.WriteLine("Message : {0}" , e.Message);
    }

  }

}

import System.*;
import System.Net.*;
import System.IO.*;
import System.Text.*;
import System.Threading.*;

public class RequestState
{
    // This class stores the state of the request.
    private static final int BUFFER_SIZE = 1024;
    public StringBuilder requestData;
    public ubyte bufferRead[];
    public WebRequest request;
    public WebResponse response;
    public Stream responseStream;

    public RequestState()
    {
        bufferRead = new ubyte[BUFFER_SIZE];
        requestData = new StringBuilder("");
        request = null;
        responseStream = null;
    } //RequestState
} //RequestState

class WebRequest_BeginGetResponse
{
    public static ManualResetEvent allDone = new ManualResetEvent(false);
    private static final int BUFFER_SIZE = 1024;

    public static void main(String[] args)
    {
        try {
            // Create a new webrequest to the mentioned URL.   
            WebRequest myWebRequest = 
                WebRequest.Create("http://www.contoso.com");
            // Please, set the proxy to a correct value. 
            WebProxy proxy = new WebProxy("myproxy:80");

            proxy.set_Credentials(new NetworkCredential("srikun", "simrin123"));
            myWebRequest.set_Proxy(proxy);
            // Create a new instance of the RequestState.
            RequestState myRequestState = new RequestState();
            // The 'WebRequest' object is associated to the 'RequestState' object.
            myRequestState.request = myWebRequest;
            // Start the Asynchronous call for response.
            IAsyncResult asyncResult = (IAsyncResult)(myWebRequest.
                BeginGetResponse(new AsyncCallback(RespCallback),
                myRequestState));
            allDone.WaitOne();
            // Release the WebResponse resource.
            myRequestState.response.Close();
            Console.Read();
        }
        catch (WebException e) {
            Console.WriteLine("WebException raised!");
            Console.WriteLine("\n{0}", e.get_Message());
            Console.WriteLine("\n{0}", e.get_Status());
        }
        catch (System.Exception e) {
            Console.WriteLine("Exception raised!");
            Console.WriteLine("Source : " + e.get_Source());
            Console.WriteLine("Message : " + e.get_Message());
        }
    } //main

    private static void RespCallback(IAsyncResult asynchronousResult)
    {
        try {
            // Set the State of request to asynchronous.
            RequestState myRequestState = (RequestState)(
                asynchronousResult.get_AsyncState());
            WebRequest myWebRequest1 = myRequestState.request;
            // End the Asynchronous response.
            myRequestState.response = myWebRequest1.EndGetResponse(
                asynchronousResult);
            // Read the response into a 'Stream' object.
            Stream responseStream = myRequestState.response.GetResponseStream();
            myRequestState.responseStream = responseStream;
            // Begin the reading of the contents of the HTML page and print it 
            // to the console.
            IAsyncResult asynchronousResultRead = responseStream.BeginRead(
                myRequestState.bufferRead, 0, BUFFER_SIZE, new AsyncCallback(
                ReadCallBack), myRequestState);
        }
        catch (WebException e) {
            Console.WriteLine("WebException raised!");
            Console.WriteLine("\n{0}", e.get_Message());
            Console.WriteLine("\n{0}", e.get_Status());
        }
        catch (System.Exception e) {
            Console.WriteLine("Exception raised!");
            Console.WriteLine("Source : " + e.get_Source());
            Console.WriteLine("Message : " + e.get_Message());
        }
    } //RespCallback

    private static void ReadCallBack(IAsyncResult asyncResult)
    {
        try {
            // Result state is set to AsyncState.
            RequestState myRequestState = (RequestState)(
                asyncResult.get_AsyncState());
            Stream responseStream = myRequestState.responseStream;
            int read = responseStream.EndRead(asyncResult);
            // Read the contents of the HTML page and then print to the console.
            if (read > 0) {
                myRequestState.requestData.Append(Encoding.get_ASCII().
                    GetString(myRequestState.bufferRead, 0, read));
                IAsyncResult asynchronousResult = responseStream.BeginRead(
                    myRequestState.bufferRead, 0, BUFFER_SIZE,
                    new AsyncCallback(ReadCallBack), myRequestState);
            }
            else {
                Console.WriteLine("\nThe HTML page Contents are:  ");
                if (myRequestState.requestData.get_Length() > 1) {
                    String sringContent;
                    sringContent = myRequestState.requestData.ToString();
                    Console.WriteLine(sringContent);
                }
                Console.WriteLine("\nPress 'Enter' key to continue........");
                responseStream.Close();
                allDone.Set();
            }
        }
        catch (WebException e) {
            Console.WriteLine("WebException raised!");
            Console.WriteLine("\n{0}", e.get_Message());
            Console.WriteLine("\n{0}", e.get_Status());
        }
        catch (System.Exception e) {
            Console.WriteLine("Exception raised!");
            Console.WriteLine("Source : {0}", e.get_Source());
            Console.WriteLine("Message : {0}", e.get_Message());
        }
    } //ReadCallBack
} //WebRequest_BeginGetResponse

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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