gridsplitter wpf边框的虚线

Question

有没有办法让我的边框而不是围绕它的实线变成虚线？我只希望它出现在左侧和右侧，顶部和底部应该没有任何东西。

<Grid Grid.IsSharedSizeScope="True">
    <Grid.ColumnDefinitions>
        <ColumnDefinition SharedSizeGroup="A" Width="Auto"/>
        <ColumnDefinition Width="Auto"/>
        <ColumnDefinition/>
        <ColumnDefinition Width="Auto"/>
        <ColumnDefinition SharedSizeGroup="A" Width="Auto"/>
    </Grid.ColumnDefinitions>

    <Label Content="Shnarf Left" Background="Azure" Grid.Column="0"/>
    <TextBlock Text="Shnarf Middle" Background="Lavender" Grid.Column="2" TextWrapping="Wrap"/>
    <Label Content="Shnarf Right" Background="Moccasin" Grid.Column="4"/>

    <GridSplitter Grid.Column="1" Width="8"
                  HorizontalAlignment="Center" VerticalAlignment="Stretch" ShowsPreview="True" BorderBrush="Black" BorderThickness="1,0,1,0"/>
    <GridSplitter Grid.Column="3" Width="8" Background="DarkSlateBlue"
                  HorizontalAlignment="Center" VerticalAlignment="Stretch" ShowsPreview="True"/>
</Grid>