How to set event trigger on toolkit DropDownButton IsOpen - wpf

Question

I have a DropDownButton (a component from the Extended WPF Toolkit) that has a ListView as dropdown content. I would like to close the Popup part as soon as the user selects an item. I thought I could achieve this through an event trigger with ListView.SelectionChanged as source event, and DropDownButton.IsOpen as target property which I would set to false.
But then I'm getting the following exception when I select an item:
Cannot resolve all property references in the property path 'IsOpen'. Verify that applicable objects support the properties.
Here is my XAML:
<ListView.Triggers>
<EventTrigger RoutedEvent="ListView.SelectionChanged" SourceName="MyListView">
<EventTrigger.Actions>
<BeginStoryboard>
<Storyboard>
<BooleanAnimationUsingKeyFrames
Storyboard.Target="{Binding Source={RelativeSource Mode=FindAncestor,AncestorType=xctk:DropDownButton}}"
Storyboard.TargetProperty="IsOpen"
FillBehavior="HoldEnd">
<DiscreteBooleanKeyFrame Value="False" KeyTime="0:0:1" />
</BooleanAnimationUsingKeyFrames>
</Storyboard>
</BeginStoryboard>
</EventTrigger.Actions>
</EventTrigger>
</ListView.Triggers>
Can anybody tell me what I'm doing wrong?

Answer 1

For those interested, here is a relatively simple solution that does not involve any code-behind.
<Window x:Class="PopupDemo.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="350" Width="525">
<Window.Resources>
<Style x:Key="MyPopupMenu" TargetType="MenuItem" >
<Setter Property="HorizontalAlignment" Value="Center" />
<Setter Property="SnapsToDevicePixels" Value="True" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="MenuItem">
<Border x:Name="Border"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}">
<Grid >
<ContentPresenter ContentSource="Header" />
<Rectangle x:Name="overlay"
Fill="Black"
IsHitTestVisible="False"
Visibility="Hidden"
Opacity="0.1" >
</Rectangle>
<Popup IsOpen="{Binding Path=IsSubmenuOpen, RelativeSource={RelativeSource TemplatedParent}}" Placement="Bottom" x:Name="SubMenuPopup" Focusable="false" PopupAnimation="{DynamicResource {x:Static SystemParameters.MenuPopupAnimationKey}}">
<Border x:Name="SubMenuBorder"
Background="White"
BorderBrush="{Binding Path=Foreground, RelativeSource={RelativeSource AncestorType={x:Type Menu}}}"
BorderThickness="1" Padding="2,2,2,2">
<Grid x:Name="SubMenu" Grid.IsSharedSizeScope="True">
<!-- StackPanel holds children of the menu. This is set by IsItemsHost=True -->
<StackPanel IsItemsHost="True" KeyboardNavigation.DirectionalNavigation="Cycle"/>
</Grid>
</Border>
</Popup>
</Grid>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True" >
<Setter TargetName="overlay" Property="Visibility" Value="Visible" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</Window.Resources>
<DockPanel LastChildFill="False">
<Menu DockPanel.Dock="Top" Background="Transparent">
<MenuItem Style="{StaticResource MyPopupMenu}" >
<MenuItem.Header>
<Border Background="#3382cc" BorderThickness="12 4" BorderBrush="#3382cc">
<StackPanel Orientation="Horizontal">
<TextBlock Text="My Popup Menu" Foreground="White" />
</StackPanel>
</Border>
</MenuItem.Header>
<MenuItem Header="Alfa" />
<MenuItem Header="Bravo" />
<MenuItem Header="Charlie" />
<MenuItem Header="Delta" />
<MenuItem Header="Echo" />
</MenuItem>
</Menu>
</DockPanel>
</Window>