What happened to my data transfer binding?

Question

I created an attached property to extend the Button class with an additional state:

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

Then I want to access this value in ControlTemplateusing DataTriggeras follows:

<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>

But I get this error:

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

The hidden expression in DataTriggerseems wrong. What am I doing wrong?

Answer 1

:

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