MouseOver highlighting style returning to default after a second (Caused by Aero?)

Question

I'd trying to style my ComboBoxes to match the rest of the UI but I'm having problems with the IsMouseOver highlighting. It highlights with the color I specify for a second and then fades back to the default color, kind of a cool effect but not what I'm going for. Here is my style:

<Style TargetType="ComboBox">
    <Style.Triggers>
     <Trigger Property="ComboBox.IsMouseOver" Value="True">
      <Setter Property = "Background" Value="Red"/>
     </Trigger>
    </Style.Triggers>
</Style>

What can I do to make the background color stay?

Answer 1

The problem is indeed due to the default template for the ComboBox. If you use Reflector to open the PresentationFramework.Aero assembly you can take a look at the ButtonChrome class. There is a method called OnRenderMouseOverChanged that is hiding the Red background.

Even though it is a lot of work, for ComboBox at least, you probably will want to override the default template for the ComboBox. You can get the basic idea of what the ComboBox temlpate is like by using Show Me The Template or Blend.

You can use your same style to override the template.

<Style TargetType="{x:Type ComboBox}">
    <Setter Property="Template">
        <Setter.Value>
            <ControlTemplate TargetType="{x:Type ComboBox}">
                <!-- Template Here -->
            </ControlTemplate>
        </Setter.Value>
    </Setter>
</Style>