Avalonia/samples/ControlCatalog/Pages/CommandBarPage.xaml

<ContentPage Theme="{StaticResource ScrollPage}" xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             Header="CommandBar"
             x:Class="ControlCatalog.Pages.CommandBarPage">
  <ContentPage.Resources>
    <SolidColorBrush x:Key="NavigationBarBackground" Color="Transparent" />
  </ContentPage.Resources>
  <Grid>
    <NavigationPage x:Name="SampleNav" />
  </Grid>
</ContentPage>