WebRequest.BeginGetRequestStream(AsyncCallback, Object) Metoda

Definicja

Przestrzeń nazw:

System.Net

Zestaw:

System.Net.Requests.dll

Źródło:

WebRequest.cs

Po zastąpieniu w klasie potomnej udostępnia asynchroniczną wersję metody GetRequestStream().

public:
 virtual IAsyncResult ^ BeginGetRequestStream(AsyncCallback ^ callback, System::Object ^ state);

public virtual IAsyncResult BeginGetRequestStream (AsyncCallback? callback, object? state);

abstract member BeginGetRequestStream : AsyncCallback * obj -> IAsyncResult
override this.BeginGetRequestStream : AsyncCallback * obj -> IAsyncResult

Public Overridable Function BeginGetRequestStream (callback As AsyncCallback, state As Object) As IAsyncResult

Parametry

callback

AsyncCallback

Delegat AsyncCallback.

state

Object

Obiekt zawierający informacje o stanie dla tego asynchronicznego żądania.

Zwraca

IAsyncResult

IAsyncResult odwołujący się do żądania asynchronicznego.

Wyjątki

NotImplementedException

Każda próba uzyskania dostępu do metody, gdy metoda nie zostanie zastąpiona w klasie potomnej.

Przykłady

W poniższym przykładzie użyto BeginGetRequestStream do asynchronicznego uzyskania strumienia żądania.

#using <System.dll>

using namespace System;
using namespace System::Net;
using namespace System::IO;
using namespace System::Text;
using namespace System::Threading;
public ref class RequestState
{
public:

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

};

ref class WebRequest_BeginGetRequeststream
{
public:
   static ManualResetEvent^ allDone = gcnew ManualResetEvent( false );
   static void ReadCallback( IAsyncResult^ asynchronousResult )
   {
      RequestState^ myRequestState = dynamic_cast<RequestState^>(asynchronousResult->AsyncState);
      WebRequest^ myWebRequest = myRequestState->request;
      
      // End of 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.
      array<Byte>^byteArray = Encoding::UTF8->GetBytes( postData );
      
      // Write data to the stream.
      streamResponse->Write( byteArray, 0, postData->Length );
      streamResponse->Close();
      allDone->Set();
   }

};

int 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 its request field.
   RequestState^ myRequestState = gcnew RequestState;
   myRequestState->request = myWebRequest;
   myWebRequest->ContentType = "application/x-www-form-urlencoded";
   
   // Set the 'Method' prperty  to 'POST' to post data to a Uri.
   myRequestState->request->Method = "POST";
   
   // Start the Asynchronous 'BeginGetRequestStream' method call.
   IAsyncResult^ r = dynamic_cast<IAsyncResult^>(myWebRequest->BeginGetRequestStream( gcnew AsyncCallback( WebRequest_BeginGetRequeststream::ReadCallback ), myRequestState ));
   WebRequest_BeginGetRequeststream::allDone->WaitOne();
   WebResponse^ myWebResponse = myWebRequest->GetResponse();
   Console::WriteLine( "The String* entered has been posted." );
   Console::WriteLine( "Please wait for the response..." );
   Stream^ streamResponse = myWebResponse->GetResponseStream();
   StreamReader^ streamRead = gcnew StreamReader( streamResponse );
   array<Char>^readBuff = gcnew array<Char>(256);
   int count = streamRead->Read( readBuff, 0, 256 );
   Console::WriteLine( "The contents of the HTML page are " );
   while ( count > 0 )
   {
      String^ outputData = gcnew String( readBuff,0,count );
      Console::Write( outputData );
      count = streamRead->Read( readBuff, 0, 256 );
   }

   streamResponse->Close();
   streamRead->Close();
   
   // Release the HttpWebResponse Resource.
   myWebResponse->Close();
}

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 Asynchronous 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();
    }
}

Imports System.Net
Imports System.IO
Imports System.Text
Imports System.Threading

Public Class RequestState
    ' This class stores the request state of the request.
    Public request As WebRequest
    
    Public Sub New()
        request = Nothing
    End Sub
End Class


Class WebRequest_BeginGetRequeststream
    Public Shared allDone As New ManualResetEvent(False)
    
    Shared Sub Main()
          ' Create a new request.
            Dim myWebRequest As WebRequest = WebRequest.Create("http://www.contoso.com/codesnippets/next.asp")
 ' Create an instance of the RequestState and assign 
            ' myWebRequest' to it's request field.
            Dim myRequestState As 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.
            Dim r As IAsyncResult = CType(myWebRequest.BeginGetRequestStream(AddressOf ReadCallback, myRequestState), IAsyncResult)
            ' Pause the current thread until the async operation completes.
            allDone.WaitOne()
            ' Send the Post and get the response.
            Dim myWebResponse As WebResponse = myWebRequest.GetResponse()
            Console.WriteLine(ControlChars.Cr + "The string has been posted.")
            Console.WriteLine("Please wait for the response....")
            Dim streamResponse As Stream = myWebResponse.GetResponseStream()
            Dim streamRead As New StreamReader(streamResponse)
            Dim readBuff(256) As [Char]
            Dim count As Integer = streamRead.Read(readBuff, 0, 256)
            Console.WriteLine(ControlChars.Cr + "The contents of the HTML page are ")
            While count > 0
                Dim outputData As New [String](readBuff, 0, count)
                Console.WriteLine(outputData)
                count = streamRead.Read(readBuff, 0, 256)
            End While

           ' Close the Stream Object.
            streamResponse.Close()
            streamRead.Close()
            ' Release the HttpWebResponse Resource.
             myWebResponse.Close()
    End Sub
     
    Private Shared Sub ReadCallback(asynchronousResult As IAsyncResult)
            Dim myRequestState As RequestState = CType(asynchronousResult.AsyncState, RequestState)
            Dim myWebRequest As WebRequest = myRequestState.request
            ' End the request.
            Dim streamResponse As Stream = myWebRequest.EndGetRequestStream(asynchronousResult)
            ' Create a string that is to be posted to the uri.
            Console.WriteLine(ControlChars.Cr + "Please enter a string to be posted:")
            Dim postData As String = Console.ReadLine()
            Dim encoder As New ASCIIEncoding()
            ' Convert  the string into a byte array.
            Dim byteArray As Byte() = Encoding.UTF8.GetBytes(postData)
            ' Write the data to the stream.
            streamResponse.Write(byteArray, 0, postData.Length)
            streamResponse.Close()
            ' Allow the main thread to resume.
            allDone.Set()
    End Sub
End Class

Uwagi

Ostrożność

WebRequest, HttpWebRequest, ServicePointi WebClient są przestarzałe i nie należy ich używać do tworzenia nowych aplikacji. Zamiast tego użyj HttpClient.

Metoda BeginGetRequestStream uruchamia asynchroniczne żądanie strumienia używanego do wysyłania danych do zasobu internetowego. Metoda wywołania zwrotnego, która implementuje delegata AsyncCallback używa metody EndGetRequestStream w celu zwrócenia strumienia żądania.

Nuta

Klasa WebRequest jest klasą abstract. Rzeczywiste zachowanie wystąpień WebRequest w czasie wykonywania jest określane przez klasę potomną zwracaną przez metodę WebRequest.Create. Aby uzyskać więcej informacji na temat wartości domyślnych i wyjątków, zobacz dokumentację klas potomnych, takich jak HttpWebRequest i FileWebRequest.

Zobacz też

• EndGetRequestStream(IAsyncResult)
• wykonywanie żądań asynchronicznych