private async void videoURL_TextChanged(object sender, TextChangedEventArgs e) { if (VideoLink.IsValidLink(videoURL.Text)) { debug.Content = "ValidLink"; vaildLink = true; BitmapImage image = await WebHelper.GetThumbnailAsync(videoURL.Text, progress); VideoThumbnail_Image.Source = image; AvailableFormats.Clear(); videoQuailty_List.Items.Clear(); lister.RunWorkerAsync(argument: videoURL.Text); } else { debug.Content = "NotValidLink"; vaildLink = false; } }