圆形窗口阴影效果WPF

Question

我有以下窗口代码，该代码在透明正方形窗口内具有圆形边框，从而产生了圆形窗口的效果。如何获得圆形阴影，该阴影实际上是圆形向右下角的偏移。我尝试了各种阴影效果，但无法获得圆形外观阴影。

非常感谢

<Window x:Class="UserTraining.ConfirmRestartWindow"    
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"       
Title="Window1" Width="280"
AllowsTransparency="True"        
ResizeMode="NoResize" ShowInTaskbar="False" Topmost="True" 
WindowStyle="None" Height="280" Background="Transparent"
 ShowActivated="False" 
    WindowStartupLocation="CenterScreen" >

<Grid >
    <Border BorderBrush="Black" BorderThickness="1,1,1,1" CornerRadius="140,140,140,140" >           
        <Border.Background>
            <ImageBrush ImageSource="Saturn.png"></ImageBrush>
        </Border.Background>           
    </Border>               
</Grid>