public static string ArtistName(this RPMusicAlbum al)
 {
     RPMusicArtist ar = al.Artist();
     if (ar != null)
         return ar.Name;
     else
         return "Unknown Artist";
 }
 // Song =>
 public static string ArtistName(this RPMusicSong sg)
 {
     RPMusicArtist ar = sg.Artist();
     if (ar != null)
         return ar.Name;
     else
         return "Unknown Artist";
 }