in cs code:

if (PhonePivot.SelectedIndex == 0)            {                ApplicationBar = (IApplicationBar)Resources["AppBar0"];            }            else if (PhonePivot.SelectedIndex == 1)            { ApplicationBar = (IApplicationBar)Resources["AppBar1"];}            if (ApplicationBar != null)            {                ApplicationBar.BackgroundColor = System.Windows.Media.Colors.Black;                ApplicationBar.ForegroundColor = System.Windows.Media.Colors.White;            }