绑定到窗口的标题并不总是有效的

Question

我需要将两个TextBlock数据绑定到Window.Title属性。第一个通过工作

RelativeSource FindAncestor, AncestorType=Window}"

但第二个没有(它深深地嵌套在按钮ToolTip中(。

如何更改第二个，使其也显示Window的Title？

<Window ...>
<Border ...>
<Grid ...>
<Grid ...>
<!-- TEXTBLOCK BELOW WORKS -->
<TextBlock Grid.Column="2" Text="{Binding Title, RelativeSource={RelativeSource FindAncestor, AncestorType=Window}}"
HorizontalAlignment="Stretch" VerticalAlignment="Center" Foreground="White" FontSize="18px" FontStretch="UltraExpanded" />
<Button Grid.Column="3" HorizontalAlignment="Right" VerticalAlignment="Stretch"
Background="Transparent" BorderBrush="Transparent" Foreground="Transparent"
ToolTipService.InitialShowDelay="0" ToolTipService.BetweenShowDelay="0" ToolTipService.ShowDuration="60000">
<Button.ToolTip>
<ToolTip x:Name="helpButtonTooltip" Width="240" ToolTipService.InitialShowDelay="0">
<!-- TEXTBLOCK BELOW DOES NOT WORK; HOW CAN I MAKE IT WORK? -->
<TextBlock Text="{Binding Title, RelativeSource={RelativeSource FindAncestor, AncestorType=Window}}"
HorizontalAlignment="Stretch" VerticalAlignment="Center" Foreground="White" FontSize="18px" FontStretch="UltraExpanded" />

Answer 1

工具提示显示在弹出窗口中，与按钮或窗口不是同一视觉树的一部分。因此，RelativeSource和ElementName绑定不起作用。

您可以将窗口标题绑定到按钮的Tag属性，然后将工具提示TextBlock的Text绑定到PlacementTarget(即按钮(的Tag属性。

<Button Tag="{Binding Title, RelativeSource={RelativeSource FindAncestor, AncestorType=Window}}">
<Button.ToolTip>
<ToolTip>
<TextBlock Text="{Binding PlacementTarget.Tag, RelativeSource={RelativeSource AncestorType={x:Type ToolTip}}}"/>
</ToolTip>
</Button.ToolTip>
</Button>