FileWebRequest.BeginGetResponse(AsyncCallback, Object) Method

Reference

Definition

Namespace:: System.Net

Assembly:: System.Net.Requests.dll

Assembly:: System.dll

Assembly:: netstandard.dll

Source:: FileWebRequest.cs

Source:: FileWebRequest.cs

Source:: FileWebRequest.cs

Important

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Begins an asynchronous request for a file system resource.

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

Parameters

callback: AsyncCallback

The AsyncCallback delegate.

state: Object

An object that contains state information for this request.

Returns

IAsyncResult

An IAsyncResult that references the asynchronous request.

Exceptions

InvalidOperationException

The stream is already in use by a previous call to BeginGetResponse(AsyncCallback, Object).

WebException

The FileWebRequest was aborted.

Examples

The following code example uses the BeginGetResponse method to asynchronously access a file system resource.

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

Remarks

The asynchronous callback method that implements the AsyncCallback delegate uses the EndGetResponse method to return the actual FileWebResponse.

Applies to

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