绑定中的 WPF FindAncestor
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WPF FindAncestor in binding
提问by dbostream
One particular thing about FindAncestor confuses me, have a look at the example below:
FindAncestor 的一个特别之处让我感到困惑，请看下面的示例：
<Expander.HeaderTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<Label Name="headerLabel" Content="Show Contents" Padding="0" VerticalAlignment="Center" />
<Button Name="headerButton" Margin="6,0,0,0" Content="Button" Padding="6,1" />
</StackPanel>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Expander}}, Path=IsExpanded}" Value="True">
<Setter TargetName="headerLabel" Property="Content" Value="Hide Contents" />
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
</Expander.HeaderTemplate>
I use the xaml above to change the text of my custom expander header. My question is, when do I actually need to explicitly use FindAncestor when I want to use a property of an ancestor in my binding? Because the following three bindings appear to yield the same result in my scenario at least:
我使用上面的 xaml 来更改我的自定义扩展器标题的文本。我的问题是，当我想在绑定中使用祖先的属性时，我什么时候真正需要显式使用 FindAncestor？因为至少在我的场景中，以下三个绑定似乎会产生相同的结果：
Binding="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type Expander}}, Path=IsExpanded}"
Binding="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Expander}}, Path=IsExpanded}"
Binding="{Binding RelativeSource={RelativeSource AncestorType={x:Type Expander}}, Path=IsExpanded}"
I have seen lots of examples of all three, is it just a matter of personal taste?
我看过很多这三个的例子，这只是个人品味的问题吗？
回答by GazTheDestroyer
From the MSDN page about the RelativeSource.Modeproperty:
从关于该RelativeSource.Mode属性的 MSDN 页面：
If this property is not set explicitly, setting the AncestorType or the AncestorType and the AncestorLevel properties will implicitly lock this property value to FindAncestor.
如果未显式设置此属性，则设置 AncestorType 或 AncestorType 和 AncestorLevel 属性将隐式锁定此属性值到 FindAncestor。
