WPF ContextMenu：MenuItem 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>

命令绑定有效，而不是图标可见性绑定给我这个错误：

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.ContextMenu', AncestorLevel='1''. BindingExpression:Path=PlacementTarget.Tag.BothNaNc; DataItem=null; target element is 'Image' (Name=''); target property is 'Visibility' (type 'Visibility')

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。这应该有效：

<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>

如果您将 Icon 属性设置为您在 <Setter.Value> 中内联定义的 Image 元素，就像您当前所做的那样，它将继承 DataContext 来自父 Window 或 UserControl 或定义 Style 的任何地方。

WPF ContextMenu：MenuItem 图标可见性绑定错误

WPF ContextMenu: MenuItem Icon visibility binding error

c#

data-binding

wpf

visibility

contextmenu