WPF DataTemplate: Location of inflated storyboard - wpf

Question

I have a DataTemplate for an ItemsControl which is working fine. There is a DataTrigger in the DataTemplate which contains a BeginStoryboard EnterAction. I am trying to wire up the Completed event of the storyboard to something in code behind, specifically a method on the data object, but I can be flexible about that - at the moment I just want it to run any piece of C# code when the animation has completed.
Specifying a value for the Completed XAML attribute does not compile as the attribute is defined inside a template so there is no specific method to wire up to. So I will need to use code behind to wire up the event manually.
To this end I have looked at the application with Snoop to try to find where in the logical or visual tree the inflated template Storyboards end up. So far all I can see is a ContentControl created for each item, with its ContentTemplate set. The Content property of each ContentControl is set to its corresponding data object. The ContentTemplate property contains the Triggers collection which contain the EnterActions and ultimately the Storyboard. My question is, do all the items share a single template instance for their ContentTemplate property, or do they each get their own copy? If they share one, then where are the inflated triggers and storyboards created?
I've extracted the pertinent parts of my XAML:
<Style TargetType="{x:Type m:MyControl}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type m:MyControl}">
<Grid Name="ControlRoot" DataContext="{Binding RelativeSource={RelativeSource TemplatedParent}}">
<!-- ... -->
<ItemsControl ItemsSource="...">
<ItemsControl.ItemTemplate>
<DataTemplate DataType="{x:Type m:MyDataType}">
<Grid>
<Ellipse Name="IconHighlight1" Fill="{DynamicResource GoldRadialFade}" Width="70" Height="70" StrokeThickness="0" Opacity="0"/>
</Grid>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding Highlighted}" Value="True">
<DataTrigger.EnterActions>
<BeginStoryboard HandoffBehavior="Compose">
<Storyboard Name="ConnectToMe" Duration="0:0:2.5" FillBehavior="Stop">
<DoubleAnimation To="400" Duration="0:0:1.5" Storyboard.TargetName="IconHighlight1" Storyboard.TargetProperty="Height" FillBehavior="Stop" />
</Storyboard>
</BeginStoryboard>
</DataTrigger.EnterActions>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>

Answer 1

In such cases, I'd normally prefer to have a bool in the DataContext of the Item that your Storyboard is applying to and say call it AnimationCompleted
Now by modifying your Storyboard to
<Storyboard x:Key="ConnectToMe" Duration="0:0:2.5" FillBehavior="Stop">
<DoubleAnimation To="400" Duration="0:0:1.5" Storyboard.TargetName="IconHighlight1" Storyboard.TargetProperty="Height" FillBehavior="Stop" />
<BooleanAnimationUsingKeyFrames Storyboard.TargetProperty="DataContext.AnimationCompleted" FillBehavior="HoldEnd">
<DiscreteBooleanKeyFrame Value="False" KeyTime="0:0:0" />
</BooleanAnimationUsingKeyFrames>
<BooleanAnimationUsingKeyFrames Storyboard.TargetProperty="DataContext.AnimationCompleted" FillBehavior="HoldEnd">
<DiscreteBooleanKeyFrame Value="True" KeyTime="0:0:2.5" />
</BooleanAnimationUsingKeyFrames>
</Storyboard>
We toggle the bool AnimationCompleted to true at the end point of the animation. Hence in the property setter of AnimationCompleted check if the incoming value is True and trigger your corresponding function/method from there