ControlTemplate.Triggers 中的 TemplatedParent 绑定
当其文本为空时，我尝试使用 ControlTemplate 中的触发器将自定义控件的背景设置为视觉画笔。下面显示了相关代码：
<ControlTemplate.Triggers>
<Trigger Property="Text" Value="">
<Setter TargetName="MyBorder" Property="Background">
<Setter.Value>
<VisualBrush Opacity="0.4" Stretch="None" TileMode="None">
<VisualBrush.Visual>
<TextBlock Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=BackgroundText}" />
</VisualBrush.Visual>
</VisualBrush>
</Setter.Value>
</Setter>
</Trigger>
</ControlTemplate.Triggers>
但是，当文本为空时，不会应用视觉画笔。但是，如果我在代码中创建可视画笔并将其公开为依赖属性，则以下代码确实可以工作：
<ControlTemplate.Triggers>
<Trigger Property="Text" Value="">
<Setter TargetName="MyBorder" Property="Background" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=BackgroundBrush}" />
</Setter>
</Trigger>
</ControlTemplate.Triggers>
不过，我宁愿在 XAML 中定义画笔。为什么第二个绑定工作正常，而第一个绑定工作不正确？
When its text is empty, I am attempting to set the background of a custom control to a visual brush using a trigger in the ControlTemplate. The following shows the relevant code:
<ControlTemplate.Triggers>
<Trigger Property="Text" Value="">
<Setter TargetName="MyBorder" Property="Background">
<Setter.Value>
<VisualBrush Opacity="0.4" Stretch="None" TileMode="None">
<VisualBrush.Visual>
<TextBlock Text="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=BackgroundText}" />
</VisualBrush.Visual>
</VisualBrush>
</Setter.Value>
</Setter>
</Trigger>
</ControlTemplate.Triggers>
When the text is empty, however, the visual brush is not applied. However, if I create the visual brush in code and expose it as a dependency property, the following code does work:
<ControlTemplate.Triggers>
<Trigger Property="Text" Value="">
<Setter TargetName="MyBorder" Property="Background" Value="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=BackgroundBrush}" />
</Setter>
</Trigger>
</ControlTemplate.Triggers>
I would rather define the brush in XAML, though. Why does the second binding work correctly but not the first?
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您是否想创建水印文本框？如果是这样，我通过向自定义控件添加 TextBlock 来创建我的控件，然后在触发器定义中引用它。当TextBox没有焦点，并且控件中没有文本时，水印（TextBlock）将可见。一旦 TexBox 获得焦点，水印就会被隐藏。然后，水印的文本将绑定到您的BackgroundText 属性。
Are you trying to create a watermark TextBox? If so, I created mine by adding a TextBlock to the custom control, and then referenced that in the Trigger definitions. When the TextBox does not have the focus, and there is no text in the control, the Watermark (TextBlock) will be visible. Once the TexBox has the focus, the Watermark will be hidden. The text of the Watermark would then be bound to your BackgroundText property.