Csharp WPF 弹出窗口 如何在按下 ESC 键时关闭 WPF 弹出窗口

我在一个资源字典中定义了一个名为"ConextPopup"的弹出窗口，如下所示:

    <ControlTemplate x:Key="UXIconComboBoxControlTemplate" TargetType="{x:Type controls:UXIconComboBox}" >
    <ControlTemplate.Resources>
        <converters:IconComboBoxDropdownHorizontalOffsetMultiConverter x:Key="ComboBoxDropdownHorizontalOffsetConverter"/>
    </ControlTemplate.Resources>
    <Grid 
        x:Name="rootGrid"
        Width="{TemplateBinding HitAreaWidth}" 
        Height="{TemplateBinding HitAreaHeight}" 
        Background="{TemplateBinding Background}">
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="Auto"/>
        </Grid.RowDefinitions>
        <controls:ExtendedHitAreaButton 
            Grid.Row="0"
            x:Name="OpenPopupIconButton"
            IsDefault="True"
            Style="{StaticResource UXIconComboBoxButtonStyle}">
             <controls:ExtendedHitAreaButton.Triggers>
                <EventTrigger RoutedEvent="Button.Click">
                    <EventTrigger.Actions>
                        <BeginStoryboard>
                            <Storyboard>
                                <BooleanAnimationUsingKeyFrames 
                                    Storyboard.TargetName="ContextPopup" 
                                    Storyboard.TargetProperty="IsOpen">
                                    <DiscreteBooleanKeyFrame KeyTime="0:0:0.25" Value="True" />
                                </BooleanAnimationUsingKeyFrames>
                            </Storyboard>
                        </BeginStoryboard>
                    </EventTrigger.Actions>
                </EventTrigger>
            </controls:ExtendedHitAreaButton.Triggers>
        </controls:ExtendedHitAreaButton>

       <Popup 
           x:Name="ContextPopup"
           Grid.Row="1" 
           Placement="Bottom"
           PlacementTarget="{Binding ElementName=OpenPopupIconButton}"
           StaysOpen="False"
           PreviewKeyDown="ContextPopup_PreviewKeyDown">
           <Popup.HorizontalOffset>
               <MultiBinding Converter="{StaticResource ComboBoxDropdownHorizontalOffsetConverter}">
                   <Binding ElementName="OpenPopupIconButton" Path="ActualWidth"/>
                   <Binding ElementName="PopupListBox" Path="ActualWidth"/>
               </MultiBinding>
           </Popup.HorizontalOffset>
            <ListBox 
                x:Name="PopupListBox" 
                ItemsSource="{Binding ItemsSource, RelativeSource={RelativeSource TemplatedParent}}"
                ItemTemplate="{Binding ItemTemplate, RelativeSource={RelativeSource TemplatedParent}}"
                Loaded="PopupListBox_OnLoaded"
                KeyboardNavigation.IsTabStop="True"
                KeyboardNavigation.TabNavigation="Continue"
                BorderThickness="0"/>
       </Popup>
    </Grid>
    <ControlTemplate.Triggers>
        <MultiDataTrigger>
            <MultiDataTrigger.Conditions>
                <Condition Binding="{Binding IconComboBoxSemanticColorType}" Value="Default"/>
                <Condition Binding="{Binding Path=IsOpen, ElementName=ContextPopup}" Value="True" />
            </MultiDataTrigger.Conditions>
            <Setter Property="Background" Value="{DynamicResource BrushIconComboBox_Popup_Open_Background}" />
        </MultiDataTrigger>
    </ControlTemplate.Triggers>
</ControlTemplate>

该弹出窗口具有名为"ContextPopup_PreviewKeyDown"的PreviewKeyDown方法，该方法在资源字典代码隐藏文件中定义如下:

private void ContextPopup_PreviewKeyDown(object sender, KeyEventArgs e)
{
    var popupControl = sender as Popup;

    if (e.Key == Key.Escape)
    {
        popupControl.IsOpen = false;
    }
}

当弹出窗口显示时，我按下Esc按钮，并验证是否调用了ContextPopup_PreviewKeyDown方法，并且已将popupControl.IsOpen属性设置为False，但该弹出窗口并未关闭.

有谁能解释一下为什么弹出窗口不能关闭，以及该怎么办？

谢谢你的帮助.