HttpWebRequest.BeginGetRequestStream(AsyncCallback, Object) 方法

定義

開始用以寫入資料之 Stream 物件的非同步要求。

public:
 override IAsyncResult ^ BeginGetRequestStream(AsyncCallback ^ callback, System::Object ^ state);
public override IAsyncResult BeginGetRequestStream (AsyncCallback callback, object state);
public override IAsyncResult BeginGetRequestStream (AsyncCallback? callback, object? state);
override this.BeginGetRequestStream : AsyncCallback * obj -> IAsyncResult
Public Overrides Function BeginGetRequestStream (callback As AsyncCallback, state As Object) As IAsyncResult

參數

callback
AsyncCallback

AsyncCallback 委派。

state
Object

這個要求的狀態物件。

傳回

參考非同步要求的 IAsyncResult

例外狀況

Method 屬性是 GET 或 HEAD。

-或-

KeepAlivetrueAllowWriteStreamBufferingfalseContentLength 為 -1,SendChunkedfalse,且 Method 為 POST 或 PUT。

資料流正在由先前對 BeginGetRequestStream(AsyncCallback, Object) 的呼叫所使用。

-或-

TransferEncoding 設定為值,且 SendChunkedfalse

-或-

執行緒集區中的執行緒即將用盡。

要求快取驗證程式指出,可以從快取處理此要求的回應;不過,寫入資料的要求絕對不能使用快取。 如果您使用不正確實作的自訂快取驗證程式,便會發生這個例外狀況。

之前已呼叫過 Abort()

在 .NET Compact Framework 應用程式中,沒有正確取得並關閉內容長度為零的要求資料流。 如需處理零內容長度要求的詳細資訊,請參閱 .NET Compact Framework 中的網路程式設計

範例

下列程式代碼範例會 BeginGetRequestStream 使用 方法來提出數據流實例的異步要求。

#using <System.dll>

using namespace System;
using namespace System::Net;
using namespace System::IO;
using namespace System::Text;
using namespace System::Threading;
ref class HttpWebRequestBeginGetRequest
{
public:
   static ManualResetEvent^ allDone = gcnew ManualResetEvent( false );
   static void Main()
   {
      
      // Create a new HttpWebRequest object.
      HttpWebRequest^ request = dynamic_cast<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.    
      AsyncCallback^ del = gcnew AsyncCallback(GetRequestStreamCallback);
      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();
    }
      

private:
    static void GetRequestStreamCallback(IAsyncResult^ asynchronousResult)
    {
        HttpWebRequest^ request = dynamic_cast<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.
        array<Byte>^ByteArray = Encoding::UTF8->GetBytes(postData);

        // Write to the request stream.
        postStream->Write(ByteArray, 0, postData->Length);
        postStream->Close();

        // Start the asynchronous operation to get the response
        AsyncCallback^ del = gcnew AsyncCallback(GetResponseCallback);
        request->BeginGetResponse(del, request);
    }

   static void GetResponseCallback(IAsyncResult^ asynchronousResult)
   {
      HttpWebRequest^ request = dynamic_cast<HttpWebRequest^>(asynchronousResult->AsyncState);

      // End the operation
      HttpWebResponse^ response = dynamic_cast<HttpWebResponse^>(request->EndGetResponse(asynchronousResult));
      Stream^ streamResponse = response->GetResponseStream();
      StreamReader^ streamRead = gcnew StreamReader(streamResponse);
      String^ responseString = streamRead->ReadToEnd();
      Console::WriteLine(responseString);
      // Close the stream object
      streamResponse->Close();
      streamRead->Close();

      // Release the HttpWebResponse
      response->Close();
      allDone->Set();
   }
};

void main()
{
   HttpWebRequestBeginGetRequest::Main();
}
using System;
using System.Net;
using System.IO;
using System.Text;
using System.Threading;

class HttpWebRequestBeginGetRequest
{
    private static ManualResetEvent allDone = new ManualResetEvent(false);

    public static void Main(string[] args)
    {


        // Create a new HttpWebRequest object.
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://www.contoso.com/example.aspx");

        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(GetRequestStreamCallback), 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();
    }

    private static void GetRequestStreamCallback(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();

        // Start the asynchronous operation to get the response
        request.BeginGetResponse(new AsyncCallback(GetResponseCallback), request);
    }

    private static void GetResponseCallback(IAsyncResult asynchronousResult)
    {
        HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;

        // End the operation
        HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
        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();
        allDone.Set();
    }
}
Imports System.Net
Imports System.IO
Imports System.Text
Imports System.Threading

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)

        ' 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 GetRequestStreamCallback, 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()
    End Sub

    Private Shared Sub GetRequestStreamCallback(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()

        ' Start the asynchronous operation to get the response
        Dim result As IAsyncResult = _
            CType(request.BeginGetResponse(AddressOf GetResponseCallback, request), _
            IAsyncResult)
    End Sub

    Private Shared Sub GetResponseCallback(ByVal asynchronousResult As IAsyncResult)
        Dim request As HttpWebRequest = CType(asynchronousResult.AsyncState, HttpWebRequest)
        
        '  Get the response.
        Dim response As HttpWebResponse = CType(request.EndGetResponse(asynchronousResult), _
           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.
        allDone.Set()
        response.Close()
    End Sub
            
End Class

備註

方法 BeginGetRequestStream 會啟動數據流的異步要求,以用來傳送 的數據 HttpWebRequest。 異步回呼方法會 EndGetRequestStream 使用 方法來傳回實際的數據流。

方法 BeginGetRequestStream 需要一些同步設定工作,才能完成 (DNS 解析、Proxy 偵測和 TCP 套接字連線,例如在此方法變成異步之前) 。 如此一來,使用者介面 (UI) 線程上就不應該呼叫這個方法,因為可能需要相當長的時間 (最多幾分鐘的時間,視網路設定而定,) 在擲回錯誤例外狀況或方法成功之前完成初始同步設定工作。

若要深入瞭解線程集區,請參閱 受控線程集區

注意

您的應用程式無法混合特定要求的同步和異步方法。 如果您呼叫 BeginGetRequestStream 方法,則必須使用 BeginGetResponse 方法來擷取回應。

注意

在應用程式中啟用網路追蹤時,這個成員會輸出追蹤資訊。 如需詳細資訊,請參閱 .NET Framework 中的網路追蹤

適用於

另請參閱