How to bind an element to a property which belongs to the root element of a control?

问题

The question may sound a little confusing, but the problem I'm currently facing is this:

<Button x:Class="sandbox.BtnLabel"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
        x:Name="this">
    <Button.ToolTip>
        <TextBlock Background="Yellow" Text="{Binding ElementName=this, Path=LabelText}"/>
    </Button.ToolTip>
    <TextBlock Background="Yellow" Text="{Binding ElementName=this, Path=LabelText}"/>
</Button>

Only the second binding works, which sets the content of the button. The first one, which I would like to use to set the contents of the tooltip of the button (via the LabelText dependency property) does not work.

Is it possible to make the first binding work? Thanks.

回答1:

Try this:

<Button x:Class="sandbox.BtnLabel"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        x:Name="this">
  <Button.ToolTip>
    <ToolTip DataContext="{Binding Path=PlacementTarget, RelativeSource={RelativeSource Self}}">
      <TextBlock Background="Yellow"
                 Text="{Binding LabelText}" />
    </ToolTip>
  </Button.ToolTip>
  <TextBlock Background="Yellow"
             Text="{Binding ElementName=this,
                            Path=LabelText}" />
</Button>

We add a ToolTip element and assign it's DataContext as it's PlacementTarget which should then reach the TextBlock

来源：https://stackoverflow.com/questions/16924711/how-to-bind-an-element-to-a-property-which-belongs-to-the-root-element-of-a-cont