Treeview contextmenu WPF

Question

如果节点有一个孩子，我想创建一个Wpf treeview女巫上下文菜单。 然后我的xaml：

<Window.Resources>
        <ContextMenu x:Key="mNode">
            <MenuItem Background="{x:Null}" Name="ctRemove" Header="Remove" />
            <MenuItem Background="{x:Null}" Name="ctChange" Header="Change path"/>
        </ContextMenu>
    </Window.Resources>
    <Grid>
        <TreeView   x:Name="tView" HorizontalAlignment="Stretch" Height="469.97" Margin="5,10,0,0" VerticalAlignment="Top" IsHitTestVisible="True" IsTabStop="False" >
            <TreeView.ItemContainerStyle>
                <Style TargetType="TreeViewItem">
                    <EventSetter Event="TreeViewItem.PreviewMouseRightButtonDown" Handler="tView_PreviewMouseRightButtonDown"/>

                    **<Style.Triggers>
                        <Trigger Property="HasItems" Value="False">
                            <Setter  Property="ContextMenu" Value="{StaticResource mNode}"/>
                        </Trigger>
                    </Style.Triggers>
                </Style>**
            </TreeView.ItemContainerStyle>
            <TreeView.Resources>

当我右键单击任何节点时，contextmenu将永远不会显示。

任何人都可以帮助我吗？