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WebRequest.BeginGetRequestStream Method

When overridden in a descendant class, provides an asynchronous version of the GetRequestStream method.

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

public virtual IAsyncResult BeginGetRequestStream (
	AsyncCallback callback,
	Object state
)
public IAsyncResult BeginGetRequestStream (
	AsyncCallback callback, 
	Object state
)
public function BeginGetRequestStream (
	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 BeginGetRequestStream method starts an asynchronous request for a stream used to send data to an Internet resource. The callback method that implements the AsyncCallback delegate uses the EndGetRequestStream method to return the request stream.

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.

The following example uses the BeginGetRequestStream to asynchronously obtain the request stream.

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

public class RequestState
{
    // This class stores the request state of the request.
    public WebRequest request;    
    public RequestState()
    {
        request = null;
    }
}

class WebRequest_BeginGetRequeststream
{
    public static ManualResetEvent allDone= new ManualResetEvent(false);
    static void Main()
    {
            // Create a new request to the mentioned URL.    
            WebRequest myWebRequest= WebRequest.Create("http://www.contoso.com");

            // Create an instance of the RequestState and assign 
            // 'myWebRequest' to it's request field.    
            RequestState myRequestState = new RequestState();
            myRequestState.request = myWebRequest;            
            myWebRequest.ContentType="application/x-www-form-urlencoded";

            // Set the 'Method' property  to 'POST' to post data to a Uri.
            myRequestState.request.Method="POST";
            // Start the Asynchronous 'BeginGetRequestStream' method call.    
            IAsyncResult r=(IAsyncResult) myWebRequest.BeginGetRequestStream(
                new AsyncCallback(ReadCallback),myRequestState);
            // Pause the current thread until the async operation completes.
            Console.WriteLine("main thread waiting...");
            allDone.WaitOne();   
            // Assign the response object of 'WebRequest' to a 'WebResponse' variable.
            WebResponse myWebResponse = myWebRequest.GetResponse();
            Console.WriteLine("The string has been posted.");    
            Console.WriteLine("Please wait for the response...");

            Stream streamResponse = myWebResponse.GetResponseStream();
            StreamReader streamRead = new StreamReader( streamResponse );
            Char[] readBuff = new Char[256];
            int count = streamRead.Read( readBuff, 0, 256 );
            Console.WriteLine("\nThe contents of the HTML page are ");    

            while (count > 0) 
            {
                String outputData = new String(readBuff, 0, count);
                Console.Write(outputData);
                count = streamRead.Read(readBuff, 0, 256);
            }

            // Close the Stream Object.
            streamResponse.Close();
            streamRead.Close();
 

            // Release the HttpWebResponse Resource.
            myWebResponse.Close();            
    }
    private static void ReadCallback(IAsyncResult asynchronousResult)
    {
            RequestState myRequestState =(RequestState) asynchronousResult.AsyncState;
            WebRequest  myWebRequest = myRequestState.request;

            // End the Asynchronus request.
            Stream streamResponse = myWebRequest.EndGetRequestStream(asynchronousResult);

            // Create a string that is to be posted to the uri.
            Console.WriteLine("Please enter a string to be posted:");
            string postData = Console.ReadLine();
            // Convert the string into a byte array.
            byte[] byteArray = Encoding.UTF8.GetBytes(postData);

            // Write the data to the stream.
            streamResponse.Write(byteArray,0,postData.Length);
            streamResponse.Close();
            allDone.Set();
    }
}

import System.*;
import System.Net.*;
import System.IO.*;
import System.Text.*;
import System.Threading.*;
public class RequestState
{
    // This class stores the request state of the request.
    public WebRequest request;

    public RequestState()
    {
        request = null;
    } //RequestState
} //RequestState

class WebRequest_BeginGetRequeststream
{
    public static ManualResetEvent allDone = new ManualResetEvent(false);

    public static void main(String[] args)
    {
        // Create a new request to the mentioned URL.    
        WebRequest myWebRequest = WebRequest.Create("http://www.contoso.com");
        // Create an instance of the RequestState and assign 
        // 'myWebRequest' to it's request field.    
        RequestState myRequestState = new RequestState();
        myRequestState.request = myWebRequest;
        myWebRequest.set_ContentType("application/x-www-form-urlencoded");
        // Set the 'Method' property  to 'POST' to post data to a Uri.
        myRequestState.request.set_Method("POST");

        // Start the Asynchronous 'BeginGetRequestStream' method call.    
        IAsyncResult r = (IAsyncResult)(myWebRequest.BeginGetRequestStream(
            new AsyncCallback(ReadCallback), myRequestState));
        // Pause the current thread until the async operation completes.
        Console.WriteLine("main thread waiting...");
        allDone.WaitOne();
        // Assign the response object of 'WebRequest' to a 'WebResponse' 
        // variable.
        WebResponse myWebResponse = myWebRequest.GetResponse();
        Console.WriteLine("The string has been posted.");
        Console.WriteLine("Please wait for the response...");

        Stream streamResponse = myWebResponse.GetResponseStream();
        StreamReader streamRead = new StreamReader(streamResponse);
        char readBuff[] = new char[256];
        int count = streamRead.Read(readBuff, 0, 256);
        Console.WriteLine("\nThe contents of the HTML page are ");

        while (count > 0) {
            String outputData = new String(readBuff, 0, count);
            Console.Write(outputData);
            count = streamRead.Read(readBuff, 0, 256);
        }
        // Close the Stream Object.
        streamResponse.Close();
        streamRead.Close();
        // Release the HttpWebResponse Resource.
        myWebResponse.Close();
    } //main

    private static void ReadCallback(IAsyncResult asynchronousResult)
    {
        RequestState myRequestState = 
            (RequestState) asynchronousResult.get_AsyncState();
        WebRequest myWebRequest = myRequestState.request;
        // End the Asynchronus request.
        Stream streamResponse = myWebRequest.EndGetRequestStream(
            asynchronousResult);
        // Create a string that is to be posted to the uri.
        Console.WriteLine("Please enter a string to be posted:");
        String postData = Console.ReadLine();
        // Convert the string into a byte array.
        ubyte byteArray[] = Encoding.get_UTF8().GetBytes(postData);
        // Write the data to the stream.
        streamResponse.Write(byteArray, 0, postData.get_Length());
        streamResponse.Close();
        allDone.Set();
    } //ReadCallback
} //WebRequest_BeginGetRequeststream

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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