private void ExecuteMediaCommandsPlay(object sender, ExecutedRoutedEventArgs e)
        {
            e.Handled = true;
            var s = new Song((UrlInfo) e.Parameter);

            Play(s);
        }
 async void Play(Song s)
 {
     Current = s;
     var mp3 = await Current.FetchMp3();
     if (string.IsNullOrEmpty(mp3))
     {
         Prompt = "Expand url faield";
         return;
     }
     Prompt = "Fetching Music...";
     await Dispatcher.BeginInvoke(DispatcherPriority.SystemIdle, (Action)(() =>
     {
         Prompt = null;
         _player.Source = new Uri(mp3);
         _player.Play();
     }));
 }