WPF RibbonApplicationMenu：FooterPaneContent与AuxiliaryPaneContent无法识别

嘿Johan，这个错误的原因很明确——你把FooterPaneContent和AuxiliaryPaneContent放错位置啦！这两个属性是**RibbonApplicationMenu的直接属性**，但你现在把它们嵌套在了一个空的RibbonApplicationSplitMenuItem标签里面，WPF自然找不到对应的附加属性定义。

错误位置回顾 #

你原来的代码关键错误部分是这样的：

<RibbonApplicationMenu SmallImageSource="images\bestand64.png" KeyTip="A">
    <!-- 这里是各种MenuItem和SplitMenuItem -->
    <RibbonApplicationSplitMenuItem>
        <RibbonApplicationMenu.FooterPaneContent>
            <!-- Footer内容 -->
        </RibbonApplicationMenu.FooterPaneContent>
        <RibbonApplicationMenu.AuxiliaryPaneContent>
            <!-- Auxiliary内容 -->
        </RibbonApplicationMenu.AuxiliaryPaneContent>
    </RibbonApplicationSplitMenuItem>
</RibbonApplicationMenu>

修正后的正确结构 #

你需要把这两个属性元素直接移到RibbonApplicationMenu的内部，和其他RibbonApplicationMenuItem、RibbonSeparator等元素同级，不需要放在任何SplitMenuItem里。修正后的完整代码片段如下：

<Ribbon.ApplicationMenu>
<RibbonApplicationMenu SmallImageSource="images\bestand64.png" KeyTip="A">
    <!-- 主菜单选项 -->
    <RibbonApplicationMenuItem Header="New" Command="New" ImageSource="images\new16.png"></RibbonApplicationMenuItem>
    <RibbonApplicationMenuItem Header="Open" Command="Open" ImageSource="images\open16.png"></RibbonApplicationMenuItem>
    <RibbonApplicationMenuItem Header="Save" Command="Save" ImageSource="images\save16.png"></RibbonApplicationMenuItem>
    <RibbonSeparator></RibbonSeparator>
    <RibbonApplicationSplitMenuItem Header="Afdrukmogelijkheden" ImageSource="images\printer64.png">
        <RibbonApplicationMenuItem Header="Afdrukken" Command="Print" ImageSource="images\printer64.png"></RibbonApplicationMenuItem>
        <RibbonApplicationMenuItem Header="Afdrukvoorbeeld" Command="PrintPreview" ImageSource="images\preview64.png"></RibbonApplicationMenuItem>
    </RibbonApplicationSplitMenuItem>

    <!-- 直接放在RibbonApplicationMenu下，这才是正确的位置 -->
    <RibbonApplicationMenu.FooterPaneContent>
        <RibbonButton Command="Close" SmallImageSource="images\close64.png" HorizontalAlignment="Right" Label="Afsluiten"></RibbonButton>
    </RibbonApplicationMenu.FooterPaneContent>

    <RibbonApplicationMenu.AuxiliaryPaneContent>
        <RibbonGallery Name="MRUGallery" CanUserFilter="False" ScrollViewer.VerticalScrollBarVisibility="Auto" SelectionChanged="MRUGallery_SelectionChanged">
            <RibbonGalleryCategory Name="MRUGalleryCat" Header="Recent Documents">
            </RibbonGalleryCategory>
        </RibbonGallery>
    </RibbonApplicationMenu.AuxiliaryPaneContent>
</RibbonApplicationMenu>
</Ribbon.ApplicationMenu>

为什么这样改？ #

在WPF的XAML中，元素的附加属性或者属性元素必须直接归属到对应的父元素上。FooterPaneContent和AuxiliaryPaneContent是RibbonApplicationMenu用来定义底部面板和辅助面板内容的专属属性，它们的作用域就是RibbonApplicationMenu本身，不能被嵌套在其他菜单子项里。

这样调整后，WPF就能正确识别这两个属性，你遇到的错误应该就会消失啦！

内容的提问来源于stack exchange，提问作者Johan Maes