silverlight datagrid 的ColumnHeader 背景色没用解决方法

silverlight datagrid 的ColumnHeader 背景色没用
以下是代码：

<data:DataGrid.ColumnHeaderStyle>
  <Style TargetType ="prim:DataGridColumnHeader">
  <Setter Property="FontSize" Value="12"></Setter>
  <Setter Property="Background" Value="Red"></Setter>
  </Style>
  </data:DataGrid.ColumnHeaderStyle>

不变色啊，急！！！

[解决办法]

XML code

<UserControl x:Class="SilverlightApplication1.MainPage"    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:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk">    <UserControl.Resources>        <Style x:Key="DataGridColumnHeaderStyle1" TargetType="sdk:DataGridColumnHeader">            <Setter Property="Template">                <Setter.Value>                    <ControlTemplate TargetType="sdk:DataGridColumnHeader">                        <Grid x:Name="Root">                            <Grid.ColumnDefinitions>                                <ColumnDefinition/>                                <ColumnDefinition Width="Auto"/>                            </Grid.ColumnDefinitions>                            <Rectangle x:Name="BackgroundRectangle" Grid.ColumnSpan="2" Fill="#FF1F3B53" Stretch="Fill"/>                            <Rectangle x:Name="BackgroundGradient" Grid.ColumnSpan="2" Stretch="Fill" Fill="Red"/>                            <Grid HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">                                <Grid.ColumnDefinitions>                                    <ColumnDefinition/>                                    <ColumnDefinition Width="Auto"/>                                </Grid.ColumnDefinitions>                                <ContentPresenter Content="{TemplateBinding Content}"/>                            </Grid>                        </Grid>                    </ControlTemplate>                </Setter.Value>            </Setter>        </Style>    </UserControl.Resources>        <Grid x:Name="LayoutRoot" Background="White">        <sdk:DataGrid AutoGenerateColumns="False" Height="189" HorizontalAlignment="Left" Margin="42,42,0,0" Name="dataGrid1" VerticalAlignment="Top" Width="322">            <sdk:DataGrid.Columns>                <sdk:DataGridCheckBoxColumn HeaderStyle="{StaticResource DataGridColumnHeaderStyle1}" CanUserReorder="True" CanUserResize="True" CanUserSort="True" Width="Auto" Header="AAA" />                <sdk:DataGridCheckBoxColumn CanUserReorder="True" CanUserResize="True" CanUserSort="True" Width="Auto" Header="BBB" />                <sdk:DataGridCheckBoxColumn CanUserReorder="True" CanUserResize="True" CanUserSort="True" Width="Auto" Header="CCC" />                <sdk:DataGridCheckBoxColumn CanUserReorder="True" CanUserResize="True" CanUserSort="True" Width="Auto" Header="DDD" />            </sdk:DataGrid.Columns>        </sdk:DataGrid>    </Grid></UserControl>