将自定义AttachedProperty绑定到工具提示 - Bug？

Question

我想将自定义AttachedProperty的值绑定到ToolTip的内容。

该绑定工作，但只在工具提示的第二个打开。第一次打开工具提示时，绑定具有其FallbackValue。

奇怪的是，它适用于“Default”AttachedProperties，例如Grid.Row。

任何人都可以解释吗？

的代码非常简单：

<Button local:AttachedProperty.TestProperty="Now it works!" Content="Button"> 
    <Button.ToolTip> 
     <ToolTip DataContext="{Binding Path=PlacementTarget, RelativeSource={x:Static RelativeSource.Self}}"> 
      <TextBlock Text="{Binding (local:AttachedProperty.TestProperty), FallbackValue=&quot;It doesn't work&quot;}" /> 
     </ToolTip> 
    </Button.ToolTip> 
</Button> 

的AttachedProperty的代码：

public static class AttachedProperty 
{ 
    public static readonly DependencyProperty TestPropertyProperty = DependencyProperty.RegisterAttached 
    (
     "TestProperty", 
     typeof(string), 
     typeof(AttachedProperty), 
     new FrameworkPropertyMetadata 
     (
      string.Empty, 
      FrameworkPropertyMetadataOptions.Inherits 
     ) 
    ); 

    public static string GetTestProperty(FrameworkElement target) 
    { 
     return (string)target.GetValue(TestPropertyProperty); 
    } 

    public static void SetTestProperty(FrameworkElement target, string value) 
    { 
     target.SetValue(TestPropertyProperty, value); 
    } 
} 

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

编辑1：解决方案和一个新的问题：

我发现当它再次定义名称空间“local”时，它就可以工作工具提示：

<ToolTip xmlns:local="clr-namespace:Test" DataContext=... 

但

如果要想要一个风格中做到这一点，你的错误

"XMLNamespace", "Assembly" or "ClrNamespace" not found in Mapping Expression 

的XML的代码为我的新的测试项目是：

<Grid x:Name="LayoutRoot"> 
    <Grid.Resources> 
     <Style TargetType="{x:Type Button}"> 
      <Setter Property="ToolTip"> 
       <Setter.Value> 
        <ToolTip xmlns:local="clr-namespace:Test" DataContext="{Binding Path=PlacementTarget, RelativeSource={x:Static RelativeSource.Self}}" > 
       <TextBlock Text="{Binding (local:AttachedProperty.TestProperty), FallbackValue=&quot;It doesn't work&quot;}" /> 
      </ToolTip> 
       </Setter.Value> 
      </Setter> 
     </Style> 
    </Grid.Resources> 

    <Button local:AttachedProperty.TestProperty="Now it works!" Content="Button" HorizontalAlignment="Center" VerticalAlignment="Center" /> 
</Grid> 

Answer 1

我已经添加在PropertyChangedCallback一些跟踪输出（和删除Inherits标志，因为它是我们eless这里）：

public static readonly DependencyProperty TestPropertyProperty = 
    DependencyProperty.RegisterAttached(
     "TestProperty", 
     typeof(string), 
     typeof(AttachedProperty), 
     new FrameworkPropertyMetadata(
      string.Empty, 
      (o, e) => Trace.TraceInformation("Setting TestProperty = \"{1}\" on {0}", o, e.NewValue)) 
); 

Visual Studio的输出证明属性已设置之前绑定抱怨说，它无法找到：

ToolTipAttachedProperty.vshost.exe Information: 0 : Setting TestProperty = "Now it works!" on System.Windows.Controls.Button 
System.Windows.Data Warning: 40 : BindingExpression path error: '(local:AttachedProperty.TestProperty)' property not found on 'object' ''Button' (Name='')'. BindingExpression:Path=(local:AttachedProperty.TestProperty); DataItem='Button' (Name=''); target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String') 

你或许应该送这对微软。

编辑：引用您关于将工具提示放在样式中的编辑。你可以这样写：

<Grid.Resources> 
    <ToolTip xmlns:local="clr-namespace:Test" x:Key="ButtonToolTip" 
      DataContext="{Binding Path=PlacementTarget, RelativeSource={x:Static RelativeSource.Self}}"> 
     <TextBlock Text="{Binding (local:AttachedProperty.TestProperty), FallbackValue=&quot;It doesn't work&quot;}" /> 
    </ToolTip> 
    <Style TargetType="Button"> 
     <Setter Property="ToolTip" Value="{StaticResource ButtonToolTip}"/> 
    </Style> 
</Grid.Resources>