How to change image in button which is in listboxitem when fires some event?

How to change image in button which is in listboxitem when fires some event?

I'm making a page with LongListboxSelector which shows audiotracks. Each item has Button "play" and TextBlock with artist and title info. I'm using BackgroundAudioPlayer. My desire is to make next: when track is playing - image of the Button is "pause", when track is over - make its Button image "play", and make the next track's Button image "pause" (next track plays automatically). I tried somethink likes this

    public AudioListPage()     {         InitializeComponent();         BackgroundAudioPlayer.Instance.PlayStateChanged += Instance_PlayStateChanged;     }      void Instance_PlayStateChanged(object sender, EventArgs e)     {         if (BackgroundAudioPlayer.Instance.PlayerState == PlayState.Stopped)         {             IEnumerable buttons = AudioLLS.Descendants<Coding4Fun.Phone.Controls.RoundButton>();             var test = new BitmapImage(new Uri(@"/Images/appbar.transport.pause.rest.png", UriKind.Relative));              foreach (Coding4Fun.Phone.Controls.RoundButton item in buttons)             {                                    if (item.ImageSource == test)                 {                     MessageBox.Show("in new image");                     item.ImageSource = new BitmapImage(new Uri(@"/Images/appbar.transport.play.rest.png", UriKind.Relative));                     buttons.GetEnumerator().MoveNext();                     item.ImageSource = new BitmapImage(new Uri(@"/Images/appbar.transport.pause.rest.png", UriKind.Relative));                 }              }         }     } 

PlayState.Stopped fires when track ends, and next is going to start. I tried to take all buttons in my LLS using LinqToVisualTree helper in IEnumerable buttons = AudioLLS.Descendants<Coding4Fun.Phone.Controls.RoundButton>() and compare their images with test. But as I can see - I'm doing it wrong, because in block if(item.ImageSource == test) my app never comes. Please, tell me, what I'm doing wrong? And if my way to solve the problem is bad - please, tell me how to do it in easy way.

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