WPF带小箭头的按钮

<ControlTemplate x:Key="btnTpl" TargetType="RadioButton">
<StackPanel Orientation="Vertical" Height="30" Background="Transparent">
<Border Name="border" Background="#006AB8" Height="25">
<ContentPresenter Name="contentPre" VerticalAlignment="Center" HorizontalAlignment="Center" TextElement.Foreground="#FFF" TextElement.FontSize="12" Margin="0"/>
</Border>
<Path x:Name="path" HorizontalAlignment="Center" VerticalAlignment="Center" Data="M 0 0 L 6 4 L 12 0 Z">
<Path.Fill>
<SolidColorBrush Color="#006AB8" />
</Path.Fill>
</Path>
</StackPanel>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter TargetName="border" Property="Margin" Value="2 2 2 0"></Setter>
<Setter TargetName="border" Property="Height" Value="23"></Setter>
<Setter Property="TextElement.FontSize" Value="11"></Setter>
</Trigger>
<Trigger Property="IsChecked" Value="true">
<Setter TargetName="border" Property="Border.Background" Value="#15BDF7"></Setter>
<Setter TargetName="path" Property="Fill" >
<Setter.Value>
<SolidColorBrush Color="#15BDF7" />
</Setter.Value>
</Setter>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>