ItemsSource项目正在重复

Question

我有一个自定义Ribbon控件，它具有ItemsSource依赖项属性。此属性是IList<RibbonItem>的类型。我在XAML中设置ItemsSource，如下所示：

<customcontrols:Ribbon.ItemsSource>
    <customcontrols:RibbonItem x:Name="InsertRibbonItem"
                               Key="insert-item"
                               TabHeader="Insert">
        <customcontrols:RibbonItem.ItemsSource>
            <customcontrols:RibbonSection SectionHeader="Layout"
                                          SeparatorColor="#ccc" />
        </customcontrols:Ribbon.ItemsSource>
    </customcontrols:RibbonItem>
    <customcontrols:RibbonItem x:Name="DesignRibbonItem"
                               Key="design-item"
                               TabHeader="Design">
        <customcontrols:RibbonItem.ItemsSource>
            <customcontrols:RibbonSection SectionHeader="Layout"
                                          SeparatorColor="#ccc" />
        </customcontrols:RibbonItem.ItemsSource>
    </customcontrols:RibbonItem>
    <customcontrols:RibbonItem x:Name="ReviewRibbonItem"
                               Key="review-item"
                               TabHeader="Review">
        <customcontrols:RibbonItem.ItemsSource>
            <customcontrols:RibbonSection SectionHeader="Structure"
                                          SeparatorColor="#ccc" />
        </customcontrols:RibbonItem.ItemsSource>
    </customcontrols:RibbonItem>
</customcontrols:Ribbon.ItemsSource>

问题在于，由于某种原因，每个RibbonItem都会在其RibbonSection（ItemsSource类型）属性中收到所有三个IList<RibbonSection>。如果我将ItemsSource绑定到List<RibbonSection>，它就可以了。这是XAML中的一个错误，还是它应该如何表现，我应该采取不同的做法？