Question

I have a ListBox that uses a custom control as the ListBox.ItemTemplate DataTemplate.

I guess my first question (and the rest are relevant) is how to you create unique names for the children in a listbox?

I ask because I am attempting to invoke a ListBox.Resource Storyboard from codebehind. The error I am getting is that the MyShadow is not found.

<MyControl.BitmapEffect>
    <DropShadowBitmapEffect x:Name="MyShadow" ShadowDepth="5" Opacity="0.5" Softness="0.5" />
</MyControl.BitmapEffect>

My xaml storyboard is

<Storyboard x:Key="FocusedShadow">
    <!-- Shadow Animation-->
    <DoubleAnimation
         Storyboard.TargetName="MyShadow" 
         Storyboard.TargetProperty="ShadowDepth" 
         To="15" 
         Duration="0:0:.14"  />
 </Storyboard>

I think what I need to do is specify the Targetname as the name of the item (relating back to first question) and the TargetProperty should be MyShadow.Shadowdepth but I don’t know how to get there from here.

In code I am doing a storyboardobject.begin(this);

TIA

Answer 1

I had a very similar problem. basically, (I am thinking) that you are trying to animate before the visual tree is fully created. I solved this by using two techniques.

first, I Raise my animate event (which fires the Trigger in my xaml) inside of a Dispatcher.BeginInvoke(...), using a priority of ApplicationIdle (this way we are pretty sure the visual tree has been created) also, I am calling UpdateLayout() before I raise the event.

second, I am accessing the object, like so: var child = this.GetTemplatedChild("MyCanvas") to ensure that the canvas is actually there before trying to raise my event. (not so sure this helped, but the exception went away after I added this)
here is my sample code:

   this.Dispatcher.BeginInvoke(new Action(() =>
   {
      this.UpdateLayout();
      if (this.Visibility == System.Windows.Visibility.Visible)
      {
         var bzyCanvas = this.GetTemplateChild("BusyCanvas");
         if (bzyCanvas != null)
            this.RaiseEvent(new RoutedEventArgs(AnimationStarted));
      }
   }),System.Windows.Threading.DispatcherPriority.ApplicationIdle);