private void Service_DownloadComplete(object sender, DownloadAudioFile e) { if (e == null) { return; } if (e.AudioFile.Source == null) { return; } VisibilityNoDownloadsTracks = Visibility.Collapsed; Changed("VisibilityNoDownloadsTracks"); if (Music.Any(a => a == e.AudioFile)) { return; } Music.Add(e.AudioFile); Changed("Music"); }