DownloadDataCompletedEventHandler Délégué

Définition

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

Exemples

L’exemple de code suivant illustre le téléchargement d’une ressource spécifiée par l’utilisateur.

// 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 lorsque le téléchargement est terminé.

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 DownloadDataCompletedEventHandler délégué, vous identifiez la méthode qui gère l’événement. Pour associer l’événement à votre gestionnaire d’événements, ajoutez une instance du délégué à l’événement. Le gestionnaire d’événements est appelé chaque fois que l’événement se produit, sauf si vous supprimez le délégué. Pour plus d’informations sur les délégués de gestionnaire d’événements, consultez Gestion et déclenchement d’événements.