DownloadDataCompletedEventArgs Class

    // 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 ();
    }

    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 ();
        }
    }