RelativeSourceの使い方

    <StackPanel Background="Black" Margin="10,10,0,0">
        <!-- TextBlock（自身）のMarginの値を表示 -->
        <TextBlock Foreground="White" Text="{Binding Margin, RelativeSource={RelativeSource Self}}" />

        <!-- StackPanelのMarginの値を表示 -->
        <TextBlock Foreground="White" Text="{Binding Margin, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type StackPanel}}}"/>
    </StackPanel>