Avalonia/src/Avalonia.Themes.Fluent/Controls/NativeMenuBar.xaml

<ResourceDictionary xmlns="https://github.com/avaloniaui"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:local="clr-namespace:Avalonia.Themes.Fluent"
                    x:CompileBindings="True">
  <local:InverseBooleanValueConverter x:Key="AvaloniaThemesFluentNativeMenuBarInverseBooleanValueConverter" Default="True"/>
  <local:IBitmapToImageConverter x:Key="AvaloniaThemesFluentNativeMenuBarIBitmapToImageConverter"/>
  <ControlTheme x:Key="{x:Type NativeMenuBar}" TargetType="NativeMenuBar">
    <Setter Property="Template">
      <ControlTemplate>
        <Menu
          IsVisible="{Binding $parent[TopLevel].(NativeMenu.IsNativeMenuExported), Converter={StaticResource AvaloniaThemesFluentNativeMenuBarInverseBooleanValueConverter}}"
          Items="{Binding $parent[TopLevel].(NativeMenu.Menu).Items}">
          <Menu.Styles>
            <Style x:CompileBindings="False" Selector="MenuItem">
              <Setter Property="Header" Value="{Binding Header}"/>
              <Setter Property="IsEnabled" Value="{Binding IsEnabled}"/>
              <Setter Property="InputGesture" Value="{Binding Gesture}"/>
              <Setter Property="Items" Value="{Binding Menu.Items}"/>
              <Setter Property="Command" Value="{Binding Command}"/>
              <Setter Property="CommandParameter" Value="{Binding CommandParameter}"/>
              <Setter Property="(NativeMenuBar.EnableMenuItemClickForwarding)" Value="True"/>
              <!--NativeMenuItem is IBitmap and MenuItem is Image-->
              <Setter Property="Icon" Value="{Binding Icon , Converter={StaticResource AvaloniaThemesFluentNativeMenuBarIBitmapToImageConverter}}"/>
            </Style>
          </Menu.Styles>
        </Menu>
      </ControlTemplate>
    </Setter>
  </ControlTheme>
</ResourceDictionary>