FileWebRequest.BeginGetResponse(AsyncCallback, Object) Metodo

Riferimento

Definizione

Spazio dei nomi:: System.Net

Assembly:: System.Net.Requests.dll

Assembly:: System.dll

Assembly:: netstandard.dll

Origine:: FileWebRequest.cs

Origine:: FileWebRequest.cs

Origine:: FileWebRequest.cs

Importante

Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.

Avvia una richiesta asincrona di una risorsa del file system.

public:
 override IAsyncResult ^ BeginGetResponse(AsyncCallback ^ callback, System::Object ^ state);

public override IAsyncResult BeginGetResponse (AsyncCallback? callback, object? state);

public override IAsyncResult BeginGetResponse (AsyncCallback callback, object state);

override this.BeginGetResponse : AsyncCallback * obj -> IAsyncResult

Public Overrides Function BeginGetResponse (callback As AsyncCallback, state As Object) As IAsyncResult

Parametri

callback: AsyncCallback

Delegato AsyncCallback.

state: Object

Oggetto che contiene informazioni sullo stato per questa richiesta.

Restituisce

IAsyncResult

Oggetto IAsyncResult che fa riferimento alla richiesta asincrona.

Eccezioni

InvalidOperationException

Il flusso è già usato da una chiamata precedente a BeginGetResponse(AsyncCallback, Object).

WebException

FileWebRequest è stato interrotto.

Esempio

Nell'esempio di codice seguente viene usato il BeginGetResponse metodo per accedere in modo asincrono a una risorsa del file system.

public ref class RequestDeclare
{
public:
   FileWebRequest^ myFileWebRequest;
   RequestDeclare()
   {
      myFileWebRequest = nullptr;
   }

};

ref class FileWebRequest_resbeginend
{
public:
   static ManualResetEvent^ allDone = gcnew ManualResetEvent( false );
   static void RespCallback( IAsyncResult^ ar )
   {
      
      // State of request is asynchronous.
      RequestDeclare^ requestDeclare = dynamic_cast<RequestDeclare^>(ar->AsyncState);
      FileWebRequest^ myFileWebRequest = requestDeclare->myFileWebRequest;
      
      // End the Asynchronus request by calling the 'EndGetResponse()' method.
      FileWebResponse^ myFileWebResponse = dynamic_cast<FileWebResponse^>(myFileWebRequest->EndGetResponse( ar ));
      
      // Reade the response into Stream.
      StreamReader^ streamReader = gcnew StreamReader( myFileWebResponse->GetResponseStream() );
      array<Char>^readBuffer = gcnew array<Char>(256);
      int count = streamReader->Read( readBuffer, 0, 256 );
      Console::WriteLine( "The contents of the file are :\n" );
      while ( count > 0 )
      {
         String^ str = gcnew String( readBuffer,0,count );
         Console::WriteLine( str );
         count = streamReader->Read( readBuffer, 0, 256 );
      }

      streamReader->Close();
      
      // Release the response Object* resources.
      myFileWebResponse->Close();
      allDone->Set();
      Console::WriteLine( "File reading is over." );
   }

};

int main()
{
   array<String^>^args = Environment::GetCommandLineArgs();
   if ( args->Length < 2 )
   {
      Console::WriteLine( "\nPlease enter the file name as command line parameter:" );
      Console::WriteLine( "Usage:FileWebRequest_resbeginend <systemname>/<sharedfoldername>/<filename>\n" );
      Console::WriteLine( "Example:FileWebRequest_resbeginend shafeeque/shaf/hello.txt" );
   }
   else
   {
      try
      {
         
         // Place a 'Webrequest'.
         WebRequest^ myWebRequest = WebRequest::Create( String::Concat( "file://", args[ 1 ] ) );
         
         // Create an instance of the 'RequestDeclare' and associating the 'myWebRequest' to it.
         RequestDeclare^ myRequestDeclare = gcnew RequestDeclare;
         myRequestDeclare->myFileWebRequest = dynamic_cast<FileWebRequest^>(myWebRequest);
         
         // Begin the Asynchronous request for getting file content using 'BeginGetResponse()' method.
         IAsyncResult^ asyncResult = dynamic_cast<IAsyncResult^>(myRequestDeclare->myFileWebRequest->BeginGetResponse( gcnew AsyncCallback( &FileWebRequest_resbeginend::RespCallback ), myRequestDeclare ));
         FileWebRequest_resbeginend::allDone->WaitOne();
      }
      catch ( ArgumentNullException^ e ) 
      {
         Console::WriteLine( "ArgumentNullException is : {0}", e->Message );
      }
      catch ( UriFormatException^ e ) 
      {
         Console::WriteLine( "UriFormatException is : {0}", e->Message );
      }

   }
}


public class RequestDeclare
{
public FileWebRequest myFileWebRequest;	

    public RequestDeclare()
    {
        myFileWebRequest = null;
    }
}

class FileWebRequest_resbeginend
{

    public static ManualResetEvent allDone = new ManualResetEvent(false);

    static void Main(string[] args)
    {
        
        if (args.Length < 1)
        {
           Console.WriteLine("\nPlease enter the file name as command line parameter:");
           Console.WriteLine("Usage:FileWebRequest_resbeginend <systemname>/<sharedfoldername>/<filename>\nExample:FileWebRequest_resbeginend shafeeque/shaf/hello.txt");
        }
        else
        {
          try
        {

              // Place a 'Webrequest'.
              WebRequest myWebRequest= WebRequest.Create("file://"+args[0]);
              // Create an instance of the 'RequestDeclare' and associating the 'myWebRequest' to it.		
              RequestDeclare myRequestDeclare = new RequestDeclare();
              myRequestDeclare.myFileWebRequest = (FileWebRequest)myWebRequest;

              // Begin the Asynchronous request for getting file content using 'BeginGetResponse()' method.	
              IAsyncResult asyncResult =(IAsyncResult) myRequestDeclare.myFileWebRequest.BeginGetResponse(new AsyncCallback(RespCallback),myRequestDeclare);			
              allDone.WaitOne();
           }
        catch(ArgumentNullException e)
           {
              Console.WriteLine("ArgumentNullException is :"+e.Message);
           }
           catch(UriFormatException e)
          {
              Console.WriteLine("UriFormatException is :"+e.Message);
          }
       }
    }

  private static void RespCallback(IAsyncResult ar)
  {	

           // State of request is asynchronous.
            RequestDeclare requestDeclare=(RequestDeclare) ar.AsyncState;
                
            FileWebRequest  myFileWebRequest=requestDeclare.myFileWebRequest;
        
           // End the Asynchronus request by calling the 'EndGetResponse()' method.
            
            FileWebResponse myFileWebResponse = (FileWebResponse) myFileWebRequest.EndGetResponse(ar);

            // Reade the response into Stream.
            StreamReader streamReader= new StreamReader(myFileWebResponse.GetResponseStream());

            Char[] readBuffer = new Char[256];
                
            int count = streamReader.Read( readBuffer, 0, 256 );

            Console.WriteLine("The contents of the file are :\n");
    
            while (count > 0)
            {
                String str = new String(readBuffer, 0, count);
                Console.WriteLine(str);
                count = streamReader.Read(readBuffer, 0, 256);
            }
            
            streamReader.Close();
            // Release the response object resources.
            myFileWebResponse.Close();
            allDone.Set();
            Console.WriteLine("File reading is over.");	
    }
}

Public Class RequestDeclare
    Public myFileWebRequest As FileWebRequest
     
    Public Sub New()
        myFileWebRequest = Nothing
    End Sub
End Class



Class FileWebRequest_resbeginend
    
    Public Shared allDone As New ManualResetEvent(False)
    
    ' Entry point which delegates to C-style main Private Function.
    Public Overloads Shared Sub Main()
        Main(GetCommandLineArgs())
    End Sub
    
    Overloads Shared Sub Main(args() As String)
        
        If args.Length < 2 Then
            Console.WriteLine(ControlChars.Cr + "Please enter the file name as command line parameter:")
            Console.WriteLine("Usage:FileWebRequest_resbeginend " + ChrW(60) + "systemname" + ChrW(62) + "/" + ChrW(60) + "sharedfoldername" + ChrW(62) + "/" + ChrW(60) + "filename" + ChrW(62) + ControlChars.Cr + "Example:FileWebRequest_resbeginend shafeeque/shaf/hello.txt")
        
        Else
            Try

                ' Place a webrequest.
                Dim myWebRequest As WebRequest = WebRequest.Create(("file://" + args(1)))
                ' Create an instance of the 'RequestDeclare' and associating the 'myWebRequest' to it.		
                Dim myRequestDeclare As New RequestDeclare()
                myRequestDeclare.myFileWebRequest = CType(myWebRequest, FileWebRequest)
                
                ' Begin the Asynchronous request for getting file content using 'BeginGetResponse()' method.	
                 Dim asyncResult As IAsyncResult = CType(myRequestDeclare.myFileWebRequest.BeginGetResponse(AddressOf RespCallback, myRequestDeclare), IAsyncResult)
                 allDone.WaitOne()

            
            Catch e As ArgumentNullException
                Console.WriteLine(("ArgumentNullException is :" + e.Message))
            Catch e As UriFormatException
                Console.WriteLine(("UriFormatException is :" + e.Message))
            End Try
        End If
    End Sub
    
    
    Private Shared Sub RespCallback(ar As IAsyncResult)



        ' State of request is asynchronous.
        Dim requestDeclare As RequestDeclare = CType(ar.AsyncState, RequestDeclare)
        
        Dim myFileWebRequest As FileWebRequest = requestDeclare.myFileWebRequest
        
        ' End the Asynchronus request by calling the 'EndGetResponse()' method.
        Dim myFileWebResponse As FileWebResponse = CType(myFileWebRequest.EndGetResponse(ar), FileWebResponse)
        
        ' Reade the response into Stream.
        Dim streamReader As New StreamReader(myFileWebResponse.GetResponseStream())

       
        Dim readBuffer(256) As [Char]
        
        Dim count As Integer = streamReader.Read(readBuffer, 0, 256)
        
        Console.WriteLine("The contents of the file are :"+ControlChars.Cr)
        
        While count > 0
            Dim str As New [String](readBuffer, 0, count)
            Console.WriteLine(str)
            count = streamReader.Read(readBuffer, 0, 256)
        End While
         streamReader.Close()
        ' Release the response object resources.
         myFileWebResponse.Close()
        allDone.Set()
        Console.WriteLine("File reading is over.")
    End Sub
End Class

Commenti

Il metodo di callback asincrono che implementa il AsyncCallback delegato usa il EndGetResponse metodo per restituire l'effettivo FileWebResponse.

Si applica a

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