/// <summary>
/// Attempts to find a storyboard that matches the newTransition name.
/// </summary>
/// <param name="newTransition">The new transition.</param>
/// <returns>A storyboard or null, if no storyboard was found.</returns>
private Storyboard GetStoryboard(string newTransition)
{
VisualStateGroup presentationGroup = VisualStateHelper.TryGetVisualStateGroup(this, PresentationGroup);
Storyboard newStoryboard = null;
if (presentationGroup != null)
{
newStoryboard = presentationGroup.States
.OfType <VisualState>()
.Where(state => state.Name == newTransition)
.Select(state => state.Storyboard)
.FirstOrDefault();
}
return(newStoryboard);
}
/// <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 (VisualStateHelper.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;
}
}