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HttpWebRequest.BeginGetRequestStream Method

Begins an asynchronous request for a Stream instance to use to write data.

[Visual Basic]
Overrides Public Function BeginGetRequestStream( _
   ByVal callback As AsyncCallback, _
   ByVal state As Object _
) As IAsyncResult
[C#]
public override IAsyncResult BeginGetRequestStream(
 AsyncCallback callback,
 object state
);
[C++]
public: IAsyncResult* BeginGetRequestStream(
 AsyncCallback* callback,
 Object* state
);
[JScript]
public override function BeginGetRequestStream(
   callback : AsyncCallback,
 state : Object
) : IAsyncResult;

Parameters

callback
The AsyncCallback delegate.
state
The state object for this request.

Return Value

An IAsyncResult that references the asynchronous request.

Exceptions

Exception Type Condition
ProtocolViolationException The Method property is GET or HEAD.

-or-

KeepAlive is true, AllowWriteStreamBuffering is false, ContentLength is -1, SendChunked is false, and Method is POST or PUT.

InvalidOperationException The stream is being used by a previous call to BeginGetRequestStream

-or-

TransferEncoding is set to a value and SendChunked is false.

-or-

The thread pool is running out of threads.

WebException Abort was previously called.

Remarks

The BeginGetRequestStream method starts an asynchronous request for a stream used to send data for the HttpWebRequest. The asynchronous callback method uses the EndGetRequestStream method to return the actual stream.

To learn more about the thread pool, see Thread Pooling.

Example

[Visual Basic, C#, C++] The following example uses the BeginGetRequestStream method to make an asynchronous request for a stream instance.

[Visual Basic] 
Imports System
Imports System.Net
Imports System.IO
Imports System.Text
Imports System.Threading
Imports Microsoft.VisualBasic

Class HttpWebRequestBeginGetRequest
    Public Shared allDone As New ManualResetEvent(False)

    Shared Sub Main()


        ' Create a new HttpWebRequest object.
      '  Dim request As HttpWebRequest = CType(WebRequest.Create("http://www.contoso.com/example.aspx"), _
       '         HttpWebRequest)
Dim request As HttpWebRequest = CType(WebRequest.Create("http://localhost/test/PostAccepter.aspx"), _
            HttpWebRequest)
        ' Set the ContentType property.
        request.ContentType = "application/x-www-form-urlencoded"
        '  Set the Method property to 'POST' to post data to the URI.
        request.Method = "POST"
        ' Start the asynchronous operation.        
        Dim result As IAsyncResult = _
            CType(request.BeginGetRequestStream(AddressOf ReadCallback, request), IAsyncResult)
        ' Keep the main thread from continuing while the asynchronous
        ' operation completes. A real world application
        ' could do something useful such as updating its user interface. 
        allDone.WaitOne()
        '  Get the response.
        Dim response As HttpWebResponse = CType(request.GetResponse(), HttpWebResponse)
        Dim streamResponse As Stream = response.GetResponseStream()
        Dim streamRead As New StreamReader(streamResponse)
        Dim responseString As String = streamRead.ReadToEnd()
        
        Console.WriteLine(responseString)
        
        ' Close Stream object.
        streamResponse.Close()
        streamRead.Close()

        ' Release the HttpWebResponse.
        response.Close()
            
    End Sub ' Main

    Private Shared Sub ReadCallback(ByVal asynchronousResult As IAsyncResult)
        Dim request As HttpWebRequest = CType(asynchronousResult.AsyncState, HttpWebRequest)
        ' End the operation.
        Dim postStream As Stream = request.EndGetRequestStream(asynchronousResult)
        Console.WriteLine("Please enter the input data to be posted:")
        Dim postData As [String] = Console.ReadLine()
        
        '  Convert the string into byte array.
        Dim byteArray As Byte() = Encoding.UTF8.GetBytes(postData)
        ' Write to the stream.
        postStream.Write(byteArray, 0, postData.Length)
        postStream.Close()
        allDone.Set()
    End Sub ' ReadCallback

End Class ' HttpWebRequest_BeginGetRequest

[C#] 
using System;
using System.Net;
using System.IO;
using System.Text;
using System.Threading;

class HttpWebRequestBeginGetRequest
{
    public static ManualResetEvent allDone = new ManualResetEvent(false);
    public static void Main()
    {
        

            // Create a new HttpWebRequest object.
            HttpWebRequest request=(HttpWebRequest) WebRequest.Create("http://www.contoso.com/example.aspx");    
    
            // Set the ContentType property. 
            request.ContentType="application/x-www-form-urlencoded";
            // Set the Method property to 'POST' to post data to the URI.
            request.Method = "POST";
            // Start the asynchronous operation.    
            request.BeginGetRequestStream(new AsyncCallback(ReadCallback), request);    
            
            // Keep the main thread from continuing while the asynchronous
            // operation completes. A real world application
            // could do something useful such as updating its user interface. 
            allDone.WaitOne();

            // Get the response.
            HttpWebResponse response = (HttpWebResponse)request.GetResponse();
            Stream streamResponse = response.GetResponseStream();
            StreamReader streamRead = new StreamReader(streamResponse);
            string responseString = streamRead.ReadToEnd();
            Console.WriteLine(responseString);
            // Close the stream object.
            streamResponse.Close();
            streamRead.Close();
    
            // Release the HttpWebResponse.
            response.Close();
        }
    
    private static void ReadCallback(IAsyncResult asynchronousResult)
    {    
            HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
            // End the operation.
            Stream postStream = request.EndGetRequestStream(asynchronousResult);
            Console.WriteLine("Please enter the input data to be posted:");
            string postData = Console.ReadLine ();
            
            // Convert the string into a byte array.
            byte[] byteArray = Encoding.UTF8.GetBytes(postData);
            // Write to the request stream.
            postStream.Write(byteArray, 0, postData.Length);
            postStream.Close ();
            allDone.Set();    
    }

}

[C++] 
#using <mscorlib.dll>
#using <System.dll>
using namespace System;
using namespace System::Net;
using namespace System::IO;
using namespace System::Text;
using namespace System::Threading;

__gc class HttpWebRequestBeginGetRequest {
public:
   static ManualResetEvent* allDone = new ManualResetEvent(false);

public:
    static void Main() {
    
        // Create a new HttpWebRequest object.
        HttpWebRequest* request =
    dynamic_cast<HttpWebRequest*> (WebRequest::Create(S"http://www.contoso.com/example.aspx"));
        // Set the ContentType property.
        request->ContentType=S"application/x-www-form-urlencoded";
        // Set the Method property to 'POST' to post data to the Uri.
        request->Method=S"POST";
    
        // Start the asynchronous operation.    
        AsyncCallback* del =     new AsyncCallback(0,ReadCallback);
        request->BeginGetRequestStream(del, request);
        
        // Keep the main thread from continuing while the asynchronous
        // operation completes. A real world application
        // could do something useful such as updating its user interface. 
        allDone->WaitOne();
        HttpWebResponse* response =
        dynamic_cast<HttpWebResponse*>(request->GetResponse());
        Stream* streamResponse =
        response->GetResponseStream();
        StreamReader* streamRead = new StreamReader(streamResponse);
        String *responseString = streamRead->ReadToEnd();
        Console::WriteLine(responseString);
        // Close Stream object.
        streamResponse->Close();
        streamRead->Close();

        // Release the HttpWebResponse.
        response->Close();
   }
private:
   static void ReadCallback(IAsyncResult* asynchronousResult) 
   {
         HttpWebRequest * request =
            dynamic_cast<HttpWebRequest*> (asynchronousResult->AsyncState);
         // End the operation.
         Stream* postStream = request->EndGetRequestStream(asynchronousResult);
         Console::WriteLine(S"Please enter the input data to be posted:");
         String * postData = Console::ReadLine();
  
         // Convert the string into Byte array.
         Byte ByteArray[] = Encoding::UTF8->GetBytes(postData);
         // Write to the request stream.
         postStream->Write(ByteArray, 0, postData->Length);
         postStream->Close();
         allDone->Set();
     
   }

};
void main()
{
   HttpWebRequestBeginGetRequest::Main();
}

[JScript] No example is available for JScript. To view a Visual Basic, C#, or C++ example, click the Language Filter button Language Filter in the upper-left corner of the page.

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family, .NET Compact Framework, Common Language Infrastructure (CLI) Standard

See Also

HttpWebRequest Class | HttpWebRequest Members | System.Net Namespace

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