WPF/XAML: accessing element outside ControlTemplate from ControlTemplate.Trigger

I have a WPF application that has a light and a switch. When I press the switch the switch and light should change to its "ON" image and when I press again they should change to their "OFF" images. I have a single restriction: I can only do this strictly in XAML and therfore no code-behind files. The way I do this is to redefine the control template for ToggleButton. Only the light switch is in this control template (the light itself shouldn't be clickable), and that is apparently my problem. I can't access the light switch from inside the control templates triggers. I get the following error "Cannot find the Trigger target 'lightImage'. (The target must appear before any Setters, Triggers, or Conditions that use it.)"

Heres my code:

 <Image Name="lightImage" Source="Resources/LOFF.bmp" Stretch="None" Canvas.Left="82" Canvas.Top="12"/>
  <ToggleButton Canvas.Left="169" Canvas.Top="123">
    <ToggleButton.Template>
      <ControlTemplate TargetType="ToggleButton">
        <Image Name="switchImage" Source="Resources/SUp.bmp"/>
        <ControlTemplate.Triggers>
          <Trigger Property="IsChecked" Value="True">
            <Setter TargetName="switchImage" Property="Source" Value="Resources/SDown.bmp" />
开发者_JAVA百科            <Setter TargetName="lightImage" Property="Source" Value="Resources/LON.bmp"/>
          </Trigger>
          <Trigger Property="IsChecked" Value="False">
            <Setter TargetName="switchImage" Property="Source" Value="Resources/SUp.bmp"/>
            <Setter TargetName="lightImage" Property="Source" Value="Resources/LOFF.bmp"/>
          </Trigger>
        </ControlTemplate.Triggers>
      </ControlTemplate>
    </ToggleButton.Template>
  </ToggleButton>

Is there another way to do this? Cheers

---

You seem to have "onImage", but trying to reference "lightImage"?

Edit: since those triggers are inside your control template I think it looks for "lightImage" only inside that template. You should create a property for 'source' in the code behind and bind to that both in your image and button.

Edit2: if no code behind maybe you could try some relative binding along the lines of:

{Binding RelativeSource={RelativeSource
FindAncestor, AncestorType={x:Type Canvas}},
Path=lightImage.Source}

Sorry if this is completely stupid, I use Silverlight and this is only available in WPF, so only a wild guess!

Anyway, idea comes from this cheatsheet, seems you can have quite complex bindings in WPF, so worth trying a few different ones: http://www.nbdtech.com/Free/WpfBinding.pdf

---

Finally, I fixed it. I didn't consider that you could use the "IsHitTestVisible" property on the image I didn't want to be clickable. With that property I could just put the lightImage inside the controltemplate and voila.

Heres the code:

<ToggleButton Canvas.Left="81" Canvas.Top="20">
            <ToggleButton.Template>
                <ControlTemplate TargetType="ToggleButton">
                    <Canvas>
                        <Image x:Name="lightImage"  Source="Resources/LOFF.bmp" IsHitTestVisible="False" />
                        <Image x:Name="switchImage" Source="Resources/SUp.bmp" Canvas.Left="88" Canvas.Top="100"/>
                    </Canvas>
                    <ControlTemplate.Triggers>
                        <Trigger Property="IsChecked" Value="True">
                            <Setter TargetName="lightImage" Property="Source" Value="Resources/LON.bmp"/>
                            <Setter TargetName="switchImage" Property="Source" Value="Resources/SDown.bmp"/>
                        </Trigger>
                        <Trigger Property="IsChecked" Value="False">
                            <Setter TargetName="lightImage" Property="Source" Value="Resources/LOFF.bmp"/>
                            <Setter TargetName="switchImage" Property="Source" Value="Resources/SUp.bmp"/>
                        </Trigger>
                    </ControlTemplate.Triggers>
                </ControlTemplate>
            </ToggleButton.Template>
        </ToggleButton>