WPF上下文菜单:菜单项图标可见性绑定错误

Question

这是我的上下文菜单的样式：

<Style x:Key="DIOStyle" TargetType="ContentControl">
        <Setter Property="Tag" Value="{Binding Content,RelativeSource={RelativeSource Mode=Self}}"/>
        <Setter Property="ContextMenu">
            <Setter.Value>
                <ContextMenu>
                    <MenuItem Style="{StaticResource DeleteMenuItemStyle}"/>
                    <!--<MenuItem Header="Normality">
                        <MenuItem Style="{StaticResource NcMenuItemStyle}"/>
                        <MenuItem Style="{StaticResource NaMenuItemStyle}"/>
                    </MenuItem>-->
                    <MenuItem Style="{StaticResource BothContactsMenuItemStyle}"/>
                </ContextMenu>
            </Setter.Value>
        </Setter>
...

这是我的MenuItem的样式：

<Style x:Key="BothContactsMenuItemStyle" TargetType="MenuItem">
        <Setter Property="Header" Value="Both Contacts"/>
        <Setter Property="Command" Value="{Binding PlacementTarget.Tag.BothNaNcChangeCommand,RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=ContextMenu}}"/>
        <Setter Property="Icon">
            <Setter.Value>
                <Image Style="{StaticResource Tick16Style}" Visibility="{Binding PlacementTarget.Tag.BothNaNc, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=ContextMenu}, Converter={StaticResource BoolToVis}}"/>
            </Setter.Value>
        </Setter>
    </Style>

命令绑定工作正常，但图标可见性绑定显示以下错误:

系统.Windows。数据错误：4:无法找到引用“RelativeSource FindAncestor，AncestorType=”System.Windows.Controls的绑定源。上下文菜单'，祖先级别=“1”。BindingExpression:路径=PlacementTarget.Tag。两种NaNc；数据项=空；目标元素为“Image”（名称=“”）；目标属性是“可见性”（类型为“可见性”）

为什么？请注意，这是有效的：

<MenuItem Header="TEST" Visibility="{Binding PlacementTarget.Tag.BothNaNc, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=ContextMenu}, Converter={StaticResource BoolToVis}}"/>

Answer 1

您可以将Image元素定义为资源。这应该是有效的：

<Image x:Key="img" x:Shared="False"
               Style="{StaticResource Tick16Style}"
               Visibility="{Binding PlacementTarget.Tag.BothNaNc, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=ContextMenu},
                            Converter={StaticResource BoolToVis}}"/>

<Style x:Key="BothContactsMenuItemStyle" TargetType="MenuItem">
    <Setter Property="Header" Value="Both Contacts"/>
    <Setter Property="Command" Value="{Binding PlacementTarget.Tag.BothNaNcChangeCommand, RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=ContextMenu}}"/>
    <Setter Property="Icon" Value="{StaticResource img}" />
</Style>

如果将＜code＞Icon＜/code＞属性设置为在＜code＞中内联定义的＜code＞Image＜/code＞元素