WPF TextBox trigger to clear Text

I have many TextBox controls and I'm trying to write a style that clears the Text property when the Control is disabled. I don't want to have Event Handlers in code behind.

I wrote this:

<Style TargetType="{x:Type TextBox}">                            
 <Style.Triggers>
  <Trigger Property="IsEnabled" Value="False">                                    
   <Setter Property="Text" Value="{x:Null}" />
  </Trigger>                                
 </Style.Triggers>
</Style>

The problem i开发者_如何学Cs that if the TextBox is defined like:

<TextBox Text={Binding Whatever} />

then the trigger does not work (probably because it's bound) How to overcome this problem?

Because you're explicitly setting the Text in the TextBox, the style's trigger can't overwrite it. Try this:

<TextBox>
    <TextBox.Style>
        <Style TargetType="{x:Type TextBox}">
            <Setter Property="Text" Value="{Binding Whatever}" />

            <Style.Triggers>
                <Trigger Property="IsEnabled" Value="False">
                    <Setter Property="Text" Value="{x:Null}" /> 
                </Trigger>
            </Style.Triggers>
        </Style> 
    </TextBox.Style>
</TextBox>