Silverlight Dockpanel Border Style

Does anyone know how to add a border to a Dockpanel. i have this:

<Style x:Key="DockPanelStyle" TargetType="controlsToolkit:DockPanel">        
   开发者_开发知识库 <Setter Property="Border">
        <Setter.Value>
            <Border BorderBrush="Gray" BorderThickness="1"/>
        </Setter.Value>
    </Setter>
    <Setter Property="HorizontalAlignment" Value="Stretch" />
    <Setter Property="VerticalAlignment" Value="Stretch" />
</Style>

However it sends an error that Property border is not correct

thank you

You can do something like this:

<Border BorderBrush="Black" BorderThickness="4" Width="200" Height="150">
  <controlsToolkit:DockPanel ... />
</Border>