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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
)

Parameters

sender
Type: System.Object

The source of the event.

e
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 Events and Delegates.

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

    // 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 ();
    }

The following method is called when the download completes.

    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 ();
        }
    }

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1
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