DownloadDataCompletedEventHandler Délégué

Définition

Représente la méthode qui gérera l'événement DownloadDataCompleted d'un WebClient.Represents the method that will handle the DownloadDataCompleted event of a WebClient.

public delegate void DownloadDataCompletedEventHandler(System::Object ^ sender, DownloadDataCompletedEventArgs ^ e);
public delegate void DownloadDataCompletedEventHandler(object sender, DownloadDataCompletedEventArgs e);
type DownloadDataCompletedEventHandler = delegate of obj * DownloadDataCompletedEventArgs -> unit
Public Delegate Sub DownloadDataCompletedEventHandler(sender As Object, e As DownloadDataCompletedEventArgs)

Paramètres

sender
Object

Source de l'événement.The source of the event.

e
DownloadDataCompletedEventArgs

DownloadDataCompletedEventArgs contenant les données d’événement.A DownloadDataCompletedEventArgs containing event data.

Héritage
DownloadDataCompletedEventHandler

Exemples

L’exemple de code suivant illustre le téléchargement d’une ressource spécifiée par l’utilisateur.The following code example demonstrates downloading a user-specified resource.

// Sample call : DownLoadDataInBackground ("http://www.contoso.com/GameScores.html");
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.
   waiter->WaitOne();
}


// Sample call : DownLoadDataInBackground ("http://www.contoso.com/GameScores.html");
public static void DownloadDataInBackground (string address)
{
    System.Threading.AutoResetEvent waiter = new System.Threading.AutoResetEvent (false);
    WebClient client = new WebClient ();
    Uri uri = new Uri(address);

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

    // Block the main application thread. Real applications
    // can perform other tasks while waiting for the download to complete.
    waiter.WaitOne ();
}

'  Sample call : DownLoadDataInBackground ("http:' www.contoso.com/GameScores.html")
Public Shared Sub DownloadDataInBackground(ByVal address As String)

    Dim waiter As System.Threading.AutoResetEvent = New System.Threading.AutoResetEvent(False)
    Dim client As WebClient = New WebClient()

    '  Specify that the DownloadDataCallback method gets called
    '  when the download completes.
    AddHandler client.DownloadDataCompleted, AddressOf DownloadDataCallback
                Dim uri as Uri = New Uri(address)
    client.DownloadDataAsync(uri, waiter)

    '  Block the main application thread. Real applications
    '  can perform other tasks while waiting for the download to complete.
    waiter.WaitOne()
End Sub

La méthode suivante est appelée une fois le téléchargement terminé.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);
   try
   {
      
      // 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 );
      }
   }
   finally
   {
      
      // Let the main application thread resume.
      waiter->Set();
   }

}


private static void DownloadDataCallback (Object sender, DownloadDataCompletedEventArgs e)
{
    System.Threading.AutoResetEvent waiter = (System.Threading.AutoResetEvent)e.UserState;

    try
    {
        // If the request was not canceled and did not throw
        // an exception, display the resource.
        if (!e.Cancelled && e.Error == null)
        {
            byte[] data = (byte[])e.Result;
            string textData = System.Text.Encoding.UTF8.GetString (data);

            Console.WriteLine (textData);
        }
    }
    finally
    {
        // Let the main application thread resume.
        waiter.Set ();
    }
}

Private Shared Sub DownloadDataCallback(ByVal sender As Object, ByVal e As DownloadDataCompletedEventArgs)

    Dim waiter As System.Threading.AutoResetEvent = CType(e.UserState, System.Threading.AutoResetEvent)

    Try

        '  If the request was not canceled and did not throw
        '  an exception, display the resource.
        If e.Cancelled = False AndAlso e.Error Is Nothing Then

            Dim data() As Byte = CType(e.Result, Byte())
            Dim textData As String = System.Text.Encoding.UTF8.GetString(data)

            Console.WriteLine(textData)
        End If
    Finally

        '  Let the main application thread resume.
        waiter.Set()
    End Try
End Sub

Remarques

Lorsque vous créez un délégué DownloadDataCompletedEventHandler, vous identifiez la méthode qui gérera l'événement.When you create a DownloadDataCompletedEventHandler delegate, you identify the method that will handle the event. Pour associer l'événement au gestionnaire d'événements, ajoutez une instance du délégué à l'événement.To associate the event with your event handler, add an instance of the delegate to the event. Le gestionnaire d'événements est appelé chaque fois qu'un événement se produit, sauf si vous supprimez le délégué.The event handler is called whenever the event occurs, unless you remove the delegate. Pour plus d’informations sur les délégués de gestionnaires d’événements, consultez gestion et déclenchement d’événements.For more information about event handler delegates, see Handling and Raising Events.

Méthodes d’extension

GetMethodInfo(Delegate)

Obtient un objet qui représente la méthode représentée par le délégué spécifié.Gets an object that represents the method represented by the specified delegate.

S’applique à