Datacontext of ControlTemplates

Question

How does a ControlTemplate handle the datacontext?

Using the the follow Template

<ControlTemplate x:Key="ToolbarButtonHover" TargetType="Button">
    <Grid Name="backgroundGrid">
        <Image Source="{DynamicResource ResourceKey=Img}" Width="{TemplateBinding Width}" Height="{TemplateBinding Height}"></Image>
    </Grid>
    <ControlTemplate.Triggers>
        <DataTrigger Binding="{Binding Path=DataContext.ToolSelected, RelativeSource={RelativeSource TemplatedParent}}" Value="Unlink">
            <Setter TargetName="backgroundGrid" Property="Background" Value="Red" />
        </DataTrigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

with the control

<Button Content="Button" 
        Template="{StaticResource ResourceKey=ToolbarButtonHover}" 
        Height="24" Width="24" Background="Red">
    <Button.Resources>
        <ImageSource x:Key="Img">Resources/Icons/toolSelect.png</ImageSource>
    </Button.Resources>
</Button>

But this does not make the background red. I have verifyed that the value of the ToolbarViewModel Property ToolSelected is in fact Unlink by having a <Label Content="{Binding ToolSelected}"/> next to the controll. So i believe the problem is that the template does not use the correct DataContext, but I'm not sure of this. That's why i ask you for help.

The Control lies in a custom usercontrol, and the ToolbarViewModel is set as context for all of it, like so.

<UserControl.DataContext>
    <local:ToolboxView/>
</UserControl.DataContext>

Answer 1

Try removing RelativeSource from DataTrigger.Binding then it should work in current DataContext:

<DataTrigger Binding="{Binding ToolSelected}" Value="Unlink">
   <Setter TargetName="backgroundGrid" Property="Background" Value="Red" />
</DataTrigger>