WPF ListBoxの選択行の背景色がフォーカスを失うと薄い色になる動作の改善

自己解決しました。

<xaml>

<Window x:Class="MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp0802"
        mc:Ignorable="d"
        Title="MainWindow" Height="316" Width="461">

    <Window.Resources>
        <!--  IsSelectとなったListBoxItemの背景色を青でハイライトする。　ここで記述したスタイルを使わないとListBoxからフォーカスが移動すると背景色が白になってしまう  -->
       
        <!-- 参考にしたサイト　https://stackoverflow.com/questions/57553583/how-to-keep-highlighting-selected-item-of-listbox-even-listbox-lost-focus  -->
        <Style x:Key="NOuse" TargetType="{x:Type ListBoxItem}">
            <Setter Property="Template">
                <!--  Revert to the "Windows 7" style template that used "SystemColors.HighlightBrushKey" etc  -->
                <!--  "ItemBorder"　が重要な働きをしている  -->
                <Setter.Value>
                    <ControlTemplate TargetType="{x:Type ListBoxItem}">
                        <Border
                    x:Name="ItemBorder"
                    Padding="{TemplateBinding Padding}"
                    Background="{TemplateBinding Background}"
                    BorderBrush="{TemplateBinding BorderBrush}"
                    BorderThickness="{TemplateBinding BorderThickness}">
                            <ContentPresenter HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
                        </Border>

                        <ControlTemplate.Triggers>
                            <!--  Use the same colours for selected items, whether or not the control has focus  -->
                            <Trigger Property="IsSelected" Value="true">
                                <Setter TargetName="ItemBorder" Property="Background" Value="{DynamicResource {x:Static SystemColors.HighlightBrushKey}}" />
                                <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.HighlightTextBrushKey}}" />
                            </Trigger>

                            <Trigger Property="IsEnabled" Value="false">
                                <Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}" />
                            </Trigger>
                        </ControlTemplate.Triggers>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
        
    </Window.Resources>
    
    
    <Grid>
        <ListBox x:Name="LB1" HorizontalAlignment="Left" Height="132" Margin="117,107,0,0" VerticalAlignment="Top" Width="108"
                ItemContainerStyle="{StaticResource NOuse}">
        </ListBox>
        
        <ListBox x:Name="LB2" HorizontalAlignment="Left" Height="132" Margin="272,107,0,0" VerticalAlignment="Top" Width="148"
                ItemContainerStyle="{StaticResource NOuse}">
            
        </ListBox> 

        <ListBox x:Name="LB3"   Margin="10,107,374,86" 
            ItemContainerStyle="{StaticResource NOuse}">
        </ListBox>
    </Grid>
</Window>

<VB.net>
Class MainWindow


   Private Sub MainWindow_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded
      Dim l1 As ListBoxItem

      l1 = New ListBoxItem : l1.Content = "1" : Me.LB1.Items.Add(l1)
      l1 = New ListBoxItem : l1.Content = "2" : Me.LB1.Items.Add(l1)
      l1 = New ListBoxItem : l1.Content = "3" : Me.LB2.Items.Add(l1)
      l1 = New ListBoxItem : l1.Content = "4" : Me.LB2.Items.Add(l1)
      l1 = New ListBoxItem : l1.Content = "5" : Me.LB2.Items.Add(l1)
      l1 = New ListBoxItem : l1.Content = "6" : Me.LB2.Items.Add(l1)

   End Sub


   Private Sub LB1_SelectionChanged(sender As Object, e As SelectionChangedEventArgs) Handles LB1.SelectionChanged
      Me.Title = $"{Me.LB1.SelectedIndex}-{Me.LB2.SelectedIndex}"
   End Sub

   Private Sub LB2_SelectionChanged(sender As Object, e As SelectionChangedEventArgs) Handles LB2.SelectionChanged
      Me.Title = $"{Me.LB1.SelectedIndex}-{Me.LB2.SelectedIndex}"
   End Sub


End Class