The ellipse can't rotate in datatrigger - wpf

Question

I want to rotate the ellipse when ProgressBar is set to true in DataTrigger. But It isn't work.
I test the ellipse is work OK with Opacity. But it isn't work with RotateTransform. And the ellipse is also work with EventTrigger.
Which is my mistake and how I fix it.
Thanks for reading my issue.
<Ellipse Name="ProgressEllipse" Width="40" Height="40" StrokeThickness="7" Stroke="{StaticResource ProcessEllipseGradient}" Margin="5,0,0,0">
<Ellipse.RenderTransform>
<RotateTransform CenterX="20" CenterY="20" Angle="0"/>
</Ellipse.RenderTransform>
<!--<Ellipse.Triggers>
<EventTrigger RoutedEvent="Ellipse.Loaded" SourceName="ProgressEllipse">
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetName="ProgressEllipse"
Storyboard.TargetProperty="(Ellipse.RenderTransform).(RotateTransform.Angle)"
From="0"
To="360"
Duration="0:0:1"
RepeatBehavior="Forever" />
</Storyboard>
</BeginStoryboard>
</EventTrigger>
</Ellipse.Triggers>-->
<Ellipse.Style>
<Style TargetType="{x:Type Ellipse}">
<Style.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=ProgressBar}" Value="True">
<DataTrigger.EnterActions>
<BeginStoryboard>
<Storyboard>
<DoubleAnimation
Storyboard.TargetProperty="(Ellipse.RenderTransform).(RotateTransform.Angle)"
From="0"
To="1"
Duration="0:0:5"
RepeatBehavior="Forever"/>
</Storyboard>
</BeginStoryboard>
</DataTrigger.EnterActions>
</DataTrigger>
</Style.Triggers>
</Style>
</Ellipse.Style>
</Ellipse>
Addition information
Sorry WPF-it. I make my question not clear.
The Ellipse is work OK when It located in form directly. But It not work when located in a Template.
Follow is my code.
https://www.mediafire.com/?7rb8gvthx94rfiy
If I omit "RelativeSource={RelativeSource self}" in the Trigger. It will throw exception(Cannot animate '(0).(1)' on an immutable object instance)
In the sample code. I have three ellipse. The left ellipse is not work when I locate it in the template(I try to make it work, but It don't work). The center ellipse is the same code with the ellipse in template. But It work OK when I locate it directly in the form. And I test ellipse with Opacity property in the template. And It work OK. I don't know which is my mistake.
Can you give me a hand.
Thanks for reading my question

Answer 1

Ellipse.ProgressBar property does not exist in WPF. Your are probably referring some property from the underlying DataContext of Ellipse.
So change Binding="{Binding RelativeSource={RelativeSource Self}, Path=ProgressBar}" to simply Binding="{Binding Path=ProgressBar}"
Also make sure that this ProgressBar property generates property change notifications so that trigger will execute the action ...
Plus you should also have an EndStoryBoard also.
<Ellipse.Style>
<Style TargetType="{x:Type Ellipse}">
<Style.Triggers>
<DataTrigger Binding="{Binding Path=ProgressBar}"
Value="True">
<DataTrigger.EnterActions>
<BeginStoryboard Name="MyStoryboard">
<Storyboard>
<DoubleAnimation
Storyboard.TargetProperty="(Ellipse.RenderTransform).(RotateTransform.Angle)"
From="0"
To="1"
Duration="0:0:5"
RepeatBehavior="Forever"/>
</Storyboard>
</BeginStoryboard>
</DataTrigger.EnterActions>
<DataTrigger.ExitActions>
<StopStoryboard BeginStoryboardName="MyStoryboard"/>
</DataTrigger.ExitActions>
</DataTrigger>
</Style.Triggers>
</Style>
</Ellipse.Style>