C# 绑定到ItemsControl中ItemsControl的AlternationalIndex

考虑以下XAML

<ItemsControl ItemsSource="{Binding Path=MyItems, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}" AlternationCount="999" >
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <StackPanel>
                <TextBlock Text="{Binding Path=(ItemsControl.AlternationIndex), 
                                        RelativeSource={RelativeSource TemplatedParent}, 
                                        FallbackValue=FAIL, 
                                        StringFormat={}Index is {0}}" />
                <ItemsControl ItemsSource="{Binding Path=MySubItems, Mode=OneWay, UpdateSourceTrigger=PropertyChanged}">
                    <ItemsControl.ItemTemplate>
                        <DataTemplate>
                            <StackPanel>
                                <TextBlock Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ItemsControl}, AncestorLevel=1}, Path=(ItemsControl.AlternationIndex)}"/>
                                <TextBlock Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ItemsControl}, AncestorLevel=2}, Path=(ItemsControl.AlternationIndex)}"/>
                            </StackPanel>
                        </DataTemplate>
                    </ItemsControl.ItemTemplate>
                </ItemsControl>
            </StackPanel>
        </DataTemplate>
    </ItemsControl.ItemTemplate>
</ItemsControl>

有三个TextBlock节点。第一个文本块是第一个ItemsControl的直接子级，并按预期显示AlternationIndex。但是，我需要在第二个ItemsControl中更深一层的AlternationIndex。因此，我不能使用TemplatedParent，我认为我可以找到具有AncestorLevel的祖先。但是，第二个ItemsControl中的两个TextBlock节点都显示“0”

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我错过了什么？如何从第二个ItemsControl中确定第一个ItemsControl的目标？

替代索引将不在ItemsControl上，而是在其每个子项上。使用DataTemplate，ItemsControl将每个子项存储在一个ContentPresenter中，该ContentPresenter将具有AlternationIndex。您需要修改的内容：

<TextBlock Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}, AncestorLevel=2}, Path=(ItemsControl.AlternationIndex)}"/>
<TextBlock Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}, AncestorLevel=2}, Path=(ItemsControl.AlternationIndex)}"/>

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替代索引将不在ItemsControl上，而是在其每个子控件上。使用DataTemplate，ItemsControl将每个子项存储在一个ContentPresenter中，该ContentPresenter将具有AlternationIndex。您需要修改的内容：

<TextBlock Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}, AncestorLevel=2}, Path=(ItemsControl.AlternationIndex)}"/>
<TextBlock Text="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContentPresenter}, AncestorLevel=2}, Path=(ItemsControl.AlternationIndex)}"/>