RelativeSource data trigger binding not working

Question

I am trying to set the background color of a DataGridTextColumn to another color if it is read-only. I am doing so with the following code:

<DataGridTextColumn Header="Test" IsReadOnly="True">
    <DataGridTextColumn.ElementStyle>
        <Style TargetType="{x:Type TextBlock}">
            <Style.Triggers>
                <DataTrigger Binding="{Binding IsReadOnly, RelativeSource={RelativeSource Mode=FindAncestor,  AncestorType={x:Type DataGridTextColumn}}}" Value="True">
                    <Setter Property="Background" Value="LightGreen"/>
                </DataTrigger>
            </Style.Triggers>
        </Style>
    </DataGridTextColumn.ElementStyle>
</DataGridTextColumn>

I am having no luck, however removing the triggers results in the background always being light green. Is something wrong with the data trigger binding? I am relatively new to WPF but this is what I could find online. Ideally this would be in App.XAML so it would work across all columns such as this, so would there then be a way to translate this to a style? Thanks.

Edit---------

If I bind by ElementName it works:

<DataTrigger Binding="{Binding IsReadOnly, ElementName=stupid}" Value="True">
        <Setter Property="Foreground" Value="Red" />
</DataTrigger>

However I would like this to be more generic if possible. Thanks again.

Answer 1

Edit: Didn't check for a background property on DataGridTextColumn at first.

This answered your original question -

<DataGridTextColumn Header="Test" IsReadOnly="True" Binding="{Binding name}" x:Name="MyColumn">
 <DataGridTextColumn.ElementStyle>
  <Style TargetType="{x:Type TextBlock}">
   <Style.Triggers>
    <DataTrigger Binding="{Binding IsReadOnly, ElementName=MyColumn}" Value="True">
     <Setter Property="Background" Value="Orange" />
    </DataTrigger>
   </Style.Triggers>
  </Style>
 </DataGridTextColumn.ElementStyle>
</DataGridTextColumn>  

To answer your second question, the DataTrigger binding you are looking for is:

<DataTrigger Binding="{Binding IsReadOnly, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type DataGridCell}}}" Value="True">

In Summary, look for the parent DataGridCell instead of DataGridTextColumn. The reason for this is the TextBlock you are trying to style is not actually a child of DataGridTextColumn, but a child of the DataGridTextColumn's peer.