如何使Silverlight 按钮完全透明？

                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
   <Style x:Key="TransparentButton" TargetType="Button">
       <Setter Property="Background" Value="Transparent" />
       <Setter Property="BorderThickness" Value="0" />
    </Style>
</ResourceDictionary>

<UserControl xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
             d:DesignHeight="300"
             d:DesignWidth="400"
             xmlns:res="clr-namespace:YourNamespace.Resources">
    <UserControl.Resources>
       <ResourceDictionary Source="Styles.xaml" />
    </UserControl.Resources>

    <Grid x:Name="LayoutRoot">
       <Button Content="Click me"
                Style="{StaticResource TransparentButton}" />
    </Grid>
</UserControl>