BeginGetResponse Method

FileWebRequest::BeginGetResponse Method (AsyncCallback^, Object^)

 

Begins an asynchronous request for a file system resource.

Namespace:   System.Net
Assembly:  System (in System.dll)

public:
[HostProtectionAttribute(SecurityAction::LinkDemand, ExternalThreading = true)]
virtual IAsyncResult^ BeginGetResponse(
	AsyncCallback^ callback,
	Object^ state
) override

Parameters

callback
Type: System::AsyncCallback^

The AsyncCallback delegate.

state
Type: System::Object^

An object that contains state information for this request.

Return Value

Type: System::IAsyncResult^

An IAsyncResult that references the asynchronous request.

Exception Condition
InvalidOperationException

The stream is already in use by a previous call to BeginGetResponse.

WebException

The FileWebRequest was aborted.

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

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 );
      }

   }
}

.NET Framework
Available since 1.1
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