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I have a WPF application with an Expander Control. I want the Expander Control to expand ONLY based on IsMouseOver event. I was able to enable the IsMouseOver behavior by implementing the corresponding trigger in ControlTemplate.Triggers. But I can't figure out how to disable the IsPressed/OnMouseClick events. Any advice on how to do is greatly appreciated. Thanks.

scorpiotomse
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1 Answers1

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You could handle the PreviewMouseLeftButtonDown event for the ToggleButton that is called "HeaderSite" in the default template:

private void HeaderSite_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e) 
    => e.Handled = true;

XAML:

<ToggleButton x:Name="HeaderSite" PreviewMouseLeftButtonDown="HeaderSite_PreviewMouseLeftButtonDown" ContentTemplate="{TemplateBinding HeaderTemplate}" ... />

Remember that XAML is a markup language and that you should implement this kind of behaviour in a programming language such as C#.

If your template is defined in a ResourceDictionary, you should add a code-behind class to it and defined the event handler there.

mm8
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  • Thank you mm8. Your answer makes complete sense. When i enter the code, i get the error: CS1061 'App' does not contain a definition for 'HeaderSite_PreviewMouseLeftButtonDown' and no accessible extension method 'HeaderSite_PreviewMouseLeftButtonDown' accepting a first argument of type 'App' could be found (are you missing a using directive or an assembly reference?). I think this has to do with your second comment. My XAML Expander style definition is in App.xaml. What code do i need to add where to address the error? – scorpiotomse Jun 11 '20 at 16:02
  • @scorpiotomse: Where did you put the event handler? It the style is defined in `App.xaml`, the code goes in `App.xaml.cs`. – mm8 Jun 11 '20 at 16:07