/// <summary>
/// TransitionProperty property changed handler.
/// </summary>
/// <param name="d">TransitioningContentControl that changed its Transition.</param>
/// <param name="e">Event arguments.</param>
private static void OnTransitionPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
TransitioningContentControl source = (TransitioningContentControl)d;
string oldTransition = e.OldValue as string;
string newTransition = e.NewValue as string;
if (source.IsTransitioning)
{
source.AbortTransition();
}
// find new transition
Storyboard newStoryboard = source.GetStoryboard(newTransition);
// unable to find the transition.
if (newStoryboard == null)
{
// could be during initialization of xaml that presentationgroups was not yet defined
if (VisualStates.TryGetVisualStateGroup(source, PresentationGroup) == null)
{
// will delay check
source.CurrentTransition = null;
}
else
{
// revert to old value
source.SetValue(TransitionProperty, oldTransition);
throw new ArgumentException(
"TransitioningContentControl_TransitionNotFound");
}
}
else
{
source.CurrentTransition = newStoryboard;
}
}