Known Issue: Attached Property ListBox.AlternationIndex Causes Error in Designer

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Known Issue

When writing ListBoxItem triggers in a style that trigger on the ListBox.AlternationIndex attached property value, if you use the valid syntax ListBox.AlternationIndex like the first trigger below, the designer will display the following error:

Error Property 'AlternationIndex' was not found in type 'ListBox'… 

Workaround

The workaround is to use the alternate valid syntax  ItemsControl.AlternationIndex as the second trigger below does.

 <Style x:Key="alternatingWithTriggers" TargetType="{x:Type ListBoxItem}">
  <Setter Property="Background" Value="Blue"/>
  <Setter Property="Foreground" Value="White"/>
  <Style.Triggers>
    <!-- valid XAML but does not work in the designer and causes an error -->
    <Trigger Property="ListBox.AlternationIndex" Value="1">
      <Setter Property="Background" Value="CornflowerBlue"/>
      <Setter Property="Foreground" Value="Black"/>
    </Trigger>

    <!-- valid alternate XAML that works in the designer -->
    <Trigger Property="ItemsControl.AlternationIndex" Value="2">
      <Setter Property="Background" Value="LightBlue"/>
      <Setter Property="Foreground" Value="Navy"/>
    </Trigger>
  </Style.Triggers>
</Style>

Comments

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Karl Shifflett

Visual Studio Cider Team