How to open a WPF Popup when another control is clicked, using XAML markup only?

Question

I've got two controls, a TextBlock and a PopUp. When the user clicks (MouseDown) on the textblock, I want to display the popup. I would think that I could do this with an EventTrigger on the Popup, but I can't use setters in an EventTrigger, I can only start storyboards. I want to do this strictly in XAML, because the two controls are in a template and I don't know how I'd find the popup in code.

This is what conceptually I want to do, but can't because you can't put a setter in an EventTrigger (like you can with a DataTrigger):

<TextBlock x:Name="CCD">Some text</TextBlock>

<Popup>
    <Popup.Style>
        <Style>
            <Style.Triggers>
                <EventTrigger SourceName="CCD" RoutedEvent="MouseDown">
                    <Setter Property="Popup.IsOpen" Value="True" />
                </EventTrigger>
            </Style.Triggers>
        </Style>
    </Popup.Style>
...

What is the best way to show a popup strictly in XAML when an event happens on a different control?

Answer 1

I did something simple, but it works.

I used a typical ToggleButton, which I restyled as a textblock by changing its control template. Then I just bound the IsChecked property on the ToggleButton to the IsOpen property on the popup. Popup has some properties like StaysOpen that let you modify the closing behavior.

The following works in XamlPad.

 <StackPanel>
  <ToggleButton Name="button"> 
    <ToggleButton.Template>
      <ControlTemplate TargetType="ToggleButton">
        <TextBlock>Click Me Here!!</TextBlock>
      </ControlTemplate>      
    </ToggleButton.Template>
  </ToggleButton>
  <Popup IsOpen="{Binding IsChecked, ElementName=button}" StaysOpen="False">
    <Border Background="LightYellow">
      <TextBlock>I'm the popup</TextBlock>
    </Border>
  </Popup> 
 </StackPanel>