我的datatrigger綁定有什麼問題？

Question

我已經創建了一個附加屬性來擴展Button類有附加狀態：

<Button v:ExtensionHelper.OperationMode="{Binding MyObject.OperationMode}" 
     Command="{Binding MyObject.Select}" 
     Style="{StaticResource operationModeControlTemplateStyle}" /> 

然後我想用DataTrigger這樣來訪問ControlTemplate這個值：

<Style x:Key="operationModeControlTemplateStyle" TargetType="Button"> 
    <Setter Property="IsHitTestVisible" Value="true" />   
    <Setter Property="Template"> 
     <Setter.Value> 
      <ControlTemplate TargetType="Button"> 
       <Grid> 
        <Image x:Name="hand" Source="hand.png" /> 
        <Image x:Name="cross" Source="cross.png" /> 
       </Grid> 
       <ControlTemplate.Triggers> 
        <DataTrigger Binding="{Binding Path=(v:ExtensionHelper.OperationMode), RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Button}}}" Value="Manual"> 
         <Setter TargetName="cross" Property="Visibility" Value="Collapsed" /> 
         <Setter TargetName="hand" Property="Visibility" Value="Visible" /> 
        </DataTrigger> 
        <DataTrigger Binding="{Binding Path=(v:ExtensionHelper.OperationMode), RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Button}}}" Value="Disabled"> 
         <Setter TargetName="cross" Property="Visibility" Value="Visible" /> 
         <Setter TargetName="hand" Property="Visibility" Value="Collapsed" /> 
        </DataTrigger> 
        <DataTrigger Binding="{Binding Path=(v:ExtensionHelper.OperationMode), RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Button}}}" Value="Automatic"> 
         <Setter TargetName="cross" Property="Visibility" Value="Collapsed" /> 
         <Setter TargetName="hand" Property="Visibility" Value="Collapsed" /> 
        </DataTrigger> 
       </ControlTemplate.Triggers> 
      </ControlTemplate> 
     </Setter.Value> 
    </Setter> 
</Style> 

，但我得到這個錯誤：

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.Button', AncestorLevel='1''. BindingExpression:Path=(0); DataItem=null; target element is 'Button' (Name=''); target property is 'NoTarget' (type 'Object')

DataTrigger中的結合表達式似乎是inco rrect。我究竟做錯了什麼？

Answer 1

答案很簡單：

Binding="{Binding RelativeSource={RelativeSource Self}, Path=(v:ExtensionHelper.OperationMode)}"