WPF中Xaml制作渐变按钮

<Window x:Class="WpfApplication1.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid Width="160" Height="52">
    <Grid.RowDefinitions>
        <RowDefinition Height="2*" />
        <RowDefinition Height="*" />
    </Grid.RowDefinitions>
    <Rectangle Grid.RowSpan="2" RadiusX="13" RadiusY="13">
       <Rectangle.Fill>
         <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
            <GradientStop Color="Green" Offset="0" />
            <GradientStop Color="DarkGreen" Offset="1" />
        </LinearGradientBrush>
       </Rectangle.Fill>
       <Rectangle.Stroke>
           <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
             <GradientStop Color="Black" Offset="0" />
             <GradientStop Color="LightGray" Offset="1" />
          </LinearGradientBrush>
       </Rectangle.Stroke>
   </Rectangle>
   <Rectangle Margin="3,2" RadiusX="8" RadiusY="12">
      <Rectangle.Fill>
           <LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
              <GradientStop Color="#dfff" Offset="0" />
              <GradientStop Color="#0fff" Offset="1" />
           </LinearGradientBrush>
       </Rectangle.Fill>
  </Rectangle>
</Grid>
</Window>