我的datatrigger绑定有什么问题？

Question

我创建了一个附加属性来扩展具有附加状态的Button类:

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

然后,我想在访问此值,ControlTemplate使用DataTrigger这样的:

<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>

但我得到这个错误:

System.Windows.Data错误:4:无法找到绑定源,引用'RelativeSource FindAncestor,AncestorType ='System.Windows.Controls.Button',AncestorLevel ='1''.BindingExpression:路径=(0); 的DataItem = NULL; target元素是'Button'(Name =''); target属性是'NoTarget'(类型'对象')

DataTrigger似乎是不正确的绑定表达式.我究竟做错了什么？

Answer 1

答案很简单:

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