private async void DownloadProgress(DownloadOperation download)
{
     if (download.Progress.TotalBytesToReceive != 0)
                {
                    value = download.Progress.BytesReceived * 100 /             download.Progress.TotalBytesToReceive;
                    progbar.Value = value;
                }
 if (download.Progress.Status == BackgroundTransferStatus.Completed || value >= 100)
                {
//msg de completado o download
                }
}