DataTrigger change according to AttachedProperty value

Question

I am trying to change the background property in DataTemplate according to AttachedProperty value of the element, I don't get any binding errors but the Background field stay with its default value. What is the prorblem?

View:

<ContentControl common:IsOpen={Binding IsOpenValue} ContentTemplate="{StaticResource MyTemplate}"/>

DataTemplate:

<DataTemplate x:Key="MyTemplate">
  <Border Width="20" Height="20" Name="TheName"/>

  <DataTemplate.Triggers>
    <DataTrigger Binding="{Binding (common:IsOpen), RelativeSource={RelativeSource Self}}" Value=common:IsOpenEnum.Open>
      <Setter Property="Background" TargetName="TheName" Value="Red"/>
   </DataTrigger>

   <DataTrigger Binding="{Binding (common:IsOpen), RelativeSource={RelativeSource Self}}" Value=common:IsOpenEnum.Closed>
        <Setter Property="Background" TargetName="TheName" Value="Green"/>
   </DataTrigger>

  </DataTemplate.Triggers>
</DataTemplate>

Answer 1

Several issues here:

You have to use the full syntax when binding to attached properties. Something like:

<DataTrigger Binding="{Binding Path=(common:IsOpen), Rela....

Next, using RelativeSource={RelativeSource Self} will probably give you the ContentPresenter that is in the control template of the ContentControl, when you are actually looking for the property on the ContentControl. Instead, use

....RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentControl}}...

Lastly, for brevity, drop common:IsOpenEnum. from the value. Use just the value of the enum:

....Value="Open">

[I believe the lack of quotations for the value is a glitch here and that they do appear in real code]