ポップアップ内の境界線の一部を削除する方法を知りたいです。削除したい部分を写真の赤い矢印でマークしました。ご協力いただきありがとうございます。
ここにXamlコードがあります
<ControlTemplate x:Key="{ComponentResourceKey ResourceId=TopLevelHeaderTemplateKey, TypeInTargetAssembly={x:Type MenuItem}}" TargetType="{x:Type MenuItem}">
<Grid SnapsToDevicePixels="true">
<Rectangle x:Name="OuterBorder"/>
<Rectangle x:Name="Bg" Fill="{TemplateBinding Background}" Stroke="{TemplateBinding BorderBrush}"/>
<Rectangle x:Name="InnerBorder"/>
<DockPanel>
<ContentPresenter x:Name="Icon" ContentSource="Icon" Margin="4,0,6,0" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" VerticalAlignment="Center"/>
<Path x:Name="GlyphPanel" Data="{StaticResource Checkmark}" Fill="{TemplateBinding Foreground}" FlowDirection="LeftToRight" Margin="7,0,0,0" Visibility="Collapsed" VerticalAlignment="Center"/>
<ContentPresenter ContentSource="Header" Margin="{TemplateBinding Padding}" RecognizesAccessKey="True" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>
</DockPanel>
<Popup x:Name="PART_Popup" AllowsTransparency="true" Focusable="false" HorizontalOffset="0" IsOpen="{Binding IsSubmenuOpen, RelativeSource={RelativeSource TemplatedParent}}" PopupAnimation="{DynamicResource {x:Static SystemParameters.MenuPopupAnimationKey}}" Placement="Bottom" VerticalOffset="-1">
<Themes:SystemDropShadowChrome x:Name="Shdw" Color="Transparent">
<Border x:Name="SubMenuBorder" BorderBrush="{StaticResource ResourceKey=MenuBorderColorBrush}" BorderThickness="1" Background="{StaticResource MenuOpenBackgroundColorBrush}">
<ScrollViewer x:Name="SubMenuScrollViewer" Margin="1,0" Style="{DynamicResource {ComponentResourceKey ResourceId=MenuScrollViewer, TypeInTargetAssembly={x:Type FrameworkElement}}}">
<Grid RenderOptions.ClearTypeHint="Enabled">
<Canvas HorizontalAlignment="Left" Height="0" VerticalAlignment="Top" Width="0">
<Rectangle x:Name="OpaqueRect" Fill="{StaticResource ResourceKey=MenuOpenBackgroundColorBrush}" Height="{Binding ActualHeight, ElementName=SubMenuBorder}" Width="{Binding ActualWidth, ElementName=SubMenuBorder}"/>
</Canvas>
<ItemsPresenter x:Name="ItemsPresenter" KeyboardNavigation.DirectionalNavigation="Cycle" Grid.IsSharedSizeScope="true" Margin="2" SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" KeyboardNavigation.TabNavigation="Cycle"/>
</Grid>
</ScrollViewer>
</Border>
</Themes:SystemDropShadowChrome>
</Popup>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsSuspendingPopupAnimation" Value="true">
<Setter Property="PopupAnimation" TargetName="PART_Popup" Value="None"/>
</Trigger>
<Trigger Property="Icon" Value="{x:Null}">
<Setter Property="Visibility" TargetName="Icon" Value="Collapsed"/>
</Trigger>
<Trigger Property="IsChecked" Value="true">
<Setter Property="Visibility" TargetName="GlyphPanel" Value="Visible"/>
<Setter Property="Visibility" TargetName="Icon" Value="Collapsed"/>
</Trigger>
<Trigger Property="HasDropShadow" SourceName="PART_Popup" Value="true">
<Setter Property="Margin" TargetName="Shdw" Value="0,0,5,5"/>
<Setter Property="Color" TargetName="Shdw" Value="#71000000"/>
</Trigger>
<Trigger Property="IsHighlighted" Value="true">
<Setter Property="Fill" TargetName="Bg" Value="{StaticResource MenuMouseOverColorBrush}"/>
<Setter Property="Stroke" TargetName="OuterBorder" Value="{StaticResource MenuMouseOverColorBrush}"/>
<Setter Property="Stroke" TargetName="InnerBorder" Value="{StaticResource MenuMouseOverColorBrush}"/>
</Trigger>
<Trigger Property="IsKeyboardFocused" Value="true">
<Setter Property="Stroke" TargetName="Bg" Value="{StaticResource MenuMouseOverColorBrush}"/>
<Setter Property="Fill" TargetName="Bg" Value="{StaticResource MenuMouseOverColorBrush}"/>
<Setter Property="Stroke" TargetName="InnerBorder" Value="{StaticResource MenuMouseOverColorBrush}"/>
</Trigger>
<Trigger Property="IsSubmenuOpen" Value="true">
<Setter Property="Stroke" TargetName="Bg" Value="{StaticResource MenuBorderColorBrush}"/>
<Setter Property="Fill" TargetName="Bg" Value="{StaticResource MenuOpenBackgroundColorBrush}"/>
<Setter Property="Stroke" TargetName="InnerBorder" Value="{StaticResource MenuBorderColorBrush}"/>
</Trigger>
<Trigger Property="IsEnabled" Value="false">
<Setter Property="Foreground" Value="#FF9A9A9A"/>
<Setter Property="Fill" TargetName="GlyphPanel" Value="#848589"/>
</Trigger>
<Trigger Property="ScrollViewer.CanContentScroll" SourceName="SubMenuScrollViewer" Value="false">
<Setter Property="Canvas.Top" TargetName="OpaqueRect" Value="{Binding VerticalOffset, ElementName=SubMenuScrollViewer}"/>
<Setter Property="Canvas.Left" TargetName="OpaqueRect" Value="{Binding HorizontalOffset, ElementName=SubMenuScrollViewer}"/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>