I have got an(other) error while trying to upgrade our large project to SL4. I didn't write the original theme and my theme knowlege isn't great. In my SL3 app I have a datagrid themed like so:

 <!--Datagrid Style-->
    <Style TargetType="datagrid:DataGrid">
        <Setter Property="RowHeaderStyle" Value="{StaticResource System.Windows.Controls.Primitives.DataGridRowHeader}"/>
        <Setter Property="RowBackground" Value="Transparent"/>
        <Setter Property="etc" Value="..."/>
    </Style>

When I upgrade to SL 4 the first line in the XAML above gives a runtime error:
Cannot find a Resource with the Name/Key System.Windows.Controls.Primitives.DataGridRowHeader

Should I handle this differently in SL4?

TIA

Mark

Example showing error:
http://walkersretreat.co.nz/files/SilverlightApplication1.zip