protected async override void OnElementPropertyChanged (object sender, System.ComponentModel.PropertyChangedEventArgs e)
{
base.OnElementPropertyChanged (sender, e);
if (e.PropertyName == StatesButton.NormalImageProperty.PropertyName) {
await SetNormalImageResource ();
} else if (e.PropertyName == StatesButton.DisableImageProperty.PropertyName) {
await SetDisableImageResource ();
} else if (e.PropertyName == StatesButton.PressedImageProperty.PropertyName) {
await SetPressImageResource ();
}
}