DownloadDataCompletedEventHandler Delegate


Represents the method that will handle the DownloadDataCompleted event of a WebClient.

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

public delegate void DownloadDataCompletedEventHandler(
	Object^ sender,
	DownloadDataCompletedEventArgs^ e


Type: System::Object^

The source of the event.

Type: System.Net::DownloadDataCompletedEventArgs^

A DownloadDataCompletedEventArgs containing event data.

When you create a DownloadDataCompletedEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event handler delegates, see NIB: Events and Delegates.

The following code example demonstrates downloading a user-specified resource.

// Sample call : DownLoadDataInBackground ("");
void DownloadDataInBackground( String^ address )
   System::Threading::AutoResetEvent^ waiter = gcnew System::Threading::AutoResetEvent( false );
   WebClient^ client = gcnew WebClient;
   Uri ^uri = gcnew Uri(address);

   // Specify that the DownloadDataCallback method gets called
   // when the download completes.
   client->DownloadDataCompleted += gcnew DownloadDataCompletedEventHandler( DownloadDataCallback );
   client->DownloadDataAsync( uri, waiter );

   // Block the main application thread. Real applications
   // can perform other tasks while waiting for the download to complete.

The following method is called when the download completes.

void DownloadDataCallback( Object^ /*sender*/, DownloadDataCompletedEventArgs^ e )
   System::Threading::AutoResetEvent^ waiter = dynamic_cast<System::Threading::AutoResetEvent^>(e->UserState);

      // If the request was not canceled and did not throw
      // an exception, display the resource.
      if (  !e->Cancelled && e->Error == nullptr )
         array<Byte>^data = dynamic_cast<array<Byte>^>(e->Result);
         String^ textData = System::Text::Encoding::UTF8->GetString( data );
         Console::WriteLine( textData );

      // Let the main application thread resume.


.NET Framework
Available since 2.0
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