Is there a way to style a row (in tree mode) which has sub-rows

[marklam]

eg in the Files sample, a way to style 'Directory' rows but not 'File' rows?

I can make a style that identifies the expander cell in these rows:

            <TreeDataGrid.Styles>
                <Style Selector="TreeDataGridExpanderCell[ShowExpander=true]">
                    <Setter Property="Background" Value="Red"/>
                </Style>
            </TreeDataGrid.Styles>

but I can't style the parent row, because there's no syntax for 'a TreeDataGridCellsPresenter with a descendant TreeDataGridExpanderCell[ShowExpander=true]'

What I'm trying to achieve is something like the DataGrid, where the expander rows show only a description (and none of the other columns) with a different color scheme, to visually distinguish them.