带有+和 - 的WPF Expander按钮样式

<Expander Header="Expander" Name="MyExpander" IsExpanded="True">
    <TextBlock>这是一个可展开和折叠的内容区域。</TextBlock>
</Expander>

                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
   <Style x:Key="CustomExpanderStyle" TargetType="{x:Type Expander}">
       <Setter Property="HeaderTemplate">
           <Setter.Value>
                <DataTemplate>
                    <Grid Width="20" Height="20">
                        <TextBlock Text="{Binding}" VerticalAlignment="Center" HorizontalAlignment="Center"/>
                        <Path Name="ExpanderButton" Data="M0,0 L10,10 L20,0" Stroke="Black" StrokeThickness="2"
                              HorizontalAlignment="Right" VerticalAlignment="Center" Margin="0,0,5,0"/>
                    </Grid>
                    <DataTemplate.Triggers>
                        <DataTrigger Binding="{Binding ElementName=MyExpander, Path=IsExpanded}" Value="True">
                           <Setter TargetName="ExpanderButton" Property="RenderTransform">
                               <Setter.Value>
                                    <RotateTransform Angle="180"/>
                                </Setter.Value>
                            </Setter>
                        </DataTrigger>
                    </DataTemplate.Triggers>
                </DataTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>

   <ResourceDictionary Source="CustomExpanderStyle.xaml"/>
</Application.Resources>

<Expander Header="Expander" Name="MyExpander" IsExpanded="True" Style="{StaticResource CustomExpanderStyle}">
    <TextBlock>这是一个可展开和折叠的内容区域。</TextBlock>
</Expander>