如何在WPF数据模板触发器中切换Polygon的Points集合？

我希望通过WPF数据模板触发器显示不同的Polygon（注：不用在意Circle的顶点集合，我知道它完全不像圆形 ;-)）

我最初在资源中定义了两个Polygon和一个空Polygon：

<ContentControl.Resources>
    <Polygon 
        x:Key="Circle"  
        Grid.Column="0" 
        Stretch="Fill" Stroke="Black" StrokeThickness="1" Fill="DarkGray"
        Width="25" Height="25" Points=" 0,50 25,100 75,100" />        
    <Polygon 
        x:Key="Hexagon" 
        Grid.Column="0" 
        Stretch="Fill" Stroke="Black" StrokeThickness="1" Fill="DarkGray"
        Width="25" Height="25" Points=" 0,50 25,100 75,100 100,50 75,0 25,0 0,50" />

    <Polygon Name="path" Grid.Column="0" Stretch="Fill" Stroke="Black" StrokeThickness="1" Fill="DarkGray"
        Width="25" Height="25" />
</ContentControl.Resources>

然后尝试用数据模板触发器切换，但抛出运行时异常——因为我把整个Polygon对象赋值给了Points属性（它需要的是PointCollection）：

<DataTemplate.Triggers>
    <DataTrigger Binding="{Binding SimulationType}" Value="{x:Static vm:SimulationType.ServerSimulated}">
        <DataTrigger.Setters>
            <Setter TargetName="path" Property="Points" Value="{StaticResource Hexagon}"/>
        </DataTrigger.Setters>
    </DataTrigger>
    <DataTrigger Binding="{Binding SimulationType}" Value="{x:Static vm:SimulationType.ServerInSimulation}">
        <DataTrigger.Setters>
            <Setter TargetName="path" Property="Points" Value="{StaticResource Circle}"/>
        </DataTrigger.Setters>
    </DataTrigger>
</DataTemplate.Triggers>

我不清楚如何在XAML中定义PointCollection，也不知道如何通过触发器实现Polygon顶点的替换，请问该如何实现需求？

有两种常用的实现方式，可根据需求选择：

方法一：定义PointCollection资源，切换Points属性 #

把原来的Polygon资源换成PointCollection，直接赋值给Polygon的Points属性：

<ContentControl.Resources>
    <!-- 定义顶点集合资源 -->
    <PointCollection x:Key="CirclePoints">0,50 25,100 75,100</PointCollection>
    <PointCollection x:Key="HexagonPoints">0,50 25,100 75,100 100,50 75,0 25,0 0,50</PointCollection>

    <!-- 共用的Polygon控件 -->
    <Polygon Name="path" Grid.Column="0" Stretch="Fill" Stroke="Black" StrokeThickness="1" Fill="DarkGray"
             Width="25" Height="25" />
</ContentControl.Resources>

<DataTemplate.Triggers>
    <DataTrigger Binding="{Binding SimulationType}" Value="{x:Static vm:SimulationType.ServerSimulated}">
        <Setter TargetName="path" Property="Points" Value="{StaticResource HexagonPoints}"/>
    </DataTrigger>
    <DataTrigger Binding="{Binding SimulationType}" Value="{x:Static vm:SimulationType.ServerInSimulation}">
        <Setter TargetName="path" Property="Points" Value="{StaticResource CirclePoints}"/>
    </DataTrigger>
</DataTemplate.Triggers>

这种方法适合所有Polygon样式（Stroke、Fill、Size等）完全一致的场景，仅切换顶点集合。

方法二：触发器切换整个Polygon控件 #

如果后续需要不同样式（比如不同填充色、边框粗细），可以直接替换整个Polygon控件：

<ContentControl.Resources>
    <Polygon x:Key="Circle"  
             Grid.Column="0" 
             Stretch="Fill" Stroke="Black" StrokeThickness="1" Fill="DarkGray"
             Width="25" Height="25" Points=" 0,50 25,100 75,100" />        
    <Polygon x:Key="Hexagon" 
             Grid.Column="0" 
             Stretch="Fill" Stroke="Black" StrokeThickness="1" Fill="DarkGray"
             Width="25" Height="25" Points=" 0,50 25,100 75,100 100,50 75,0 25,0 0,50" />
</ContentControl.Resources>

<!-- 用ContentControl承载图形，通过触发器切换Content -->
<ContentControl x:Name="shapeContainer" Content="{StaticResource Circle}"/>

<DataTemplate.Triggers>
    <DataTrigger Binding="{Binding SimulationType}" Value="{x:Static vm:SimulationType.ServerSimulated}">
        <Setter TargetName="shapeContainer" Property="Content" Value="{StaticResource Hexagon}"/>
    </DataTrigger>
    <DataTrigger Binding="{Binding SimulationType}" Value="{x:Static vm:SimulationType.ServerInSimulation}">
        <Setter TargetName="shapeContainer" Property="Content" Value="{StaticResource Circle}"/>
    </DataTrigger>
</DataTemplate.Triggers>

这种方法更灵活，每个Polygon可独立设置样式，触发器仅负责替换整个控件。

内容的提问来源于stack exchange，提问作者bas