BeginGetRequestStream Method

WebRequest.BeginGetRequestStream Method (AsyncCallback, Object)

 

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

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

[HostProtectionAttribute(SecurityAction.LinkDemand, ExternalThreading = true)]
public virtual IAsyncResult BeginGetRequestStream(
	AsyncCallback callback,
	object state
)

Parameters

callback
Type: System.AsyncCallback

The AsyncCallback delegate.

state
Type: System.Object

An object containing state information for this asynchronous request.

Return Value

Type: System.IAsyncResult

An IAsyncResult that references the asynchronous request.

Exception Condition
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.

System_CAPS_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 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();
    }
}

Universal Windows Platform
Available since 4.5
.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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