Avalonia/samples/ControlCatalog/Pages/ContentPage/ContentPageCommandBarPage.xaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             x:Class="ControlCatalog.Pages.ContentPageCommandBarPage">
  <DockPanel>
    <ScrollViewer DockPanel.Dock="Right" Width="260">
      <StackPanel Margin="12" Spacing="8">
        <TextBlock Text="Configuration" FontWeight="SemiBold" FontSize="16"
                   Foreground="{DynamicResource SystemControlHighlightAccentBrush}" />

        <TextBlock Text="Position" FontWeight="SemiBold" />
        <ComboBox x:Name="PositionCombo"
                  SelectedIndex="0"
                  HorizontalAlignment="Stretch"
                  SelectionChanged="OnPositionChanged">
          <ComboBoxItem Content="Top" />
          <ComboBoxItem Content="Bottom" />
        </ComboBox>

        <Separator />

        <TextBlock Text="Manage Items" FontWeight="SemiBold" />
        <CheckBox x:Name="UseIconCheck" Content="Use Icon (primary items)" />
        <Button Content="Add Primary Item" HorizontalAlignment="Stretch" Click="OnAddPrimary" />
        <Button Content="Add Secondary Item" HorizontalAlignment="Stretch" Click="OnAddSecondary" />
        <Button Content="Add Separator" HorizontalAlignment="Stretch" Click="OnAddSeparator" />
        <Button Content="Clear All" HorizontalAlignment="Stretch" Click="OnClearAll" />

        <Separator />

        <TextBlock Text="Navigation" FontWeight="SemiBold" />
        <Button Content="Push Page" HorizontalAlignment="Stretch" Click="OnPush" />
        <Button Content="Pop Page" HorizontalAlignment="Stretch" Click="OnPop" />

        <Separator />

        <TextBlock Text="About" FontWeight="SemiBold" />
        <StackPanel Spacing="6">
          <Grid ColumnDefinitions="Auto,*">
            <TextBlock Text="•" FontSize="12" Opacity="0.7" Margin="0,0,6,0" />
            <TextBlock Grid.Column="1"
                       Text="NavigationPage.SetTopCommandBar(page, bar): places a CommandBar inside the navigation bar area at the top."
                       FontSize="12"
                       Opacity="0.7"
                       TextWrapping="Wrap" />
          </Grid>
          <Grid ColumnDefinitions="Auto,*">
            <TextBlock Text="•" FontSize="12" Opacity="0.7" Margin="0,0,6,0" />
            <TextBlock Grid.Column="1"
                       Text="NavigationPage.SetBottomCommandBar(page, bar): places a CommandBar below the page content at the bottom."
                       FontSize="12"
                       Opacity="0.7"
                       TextWrapping="Wrap" />
          </Grid>
          <Grid ColumnDefinitions="Auto,*">
            <TextBlock Text="•" FontSize="12" Opacity="0.7" Margin="0,0,6,0" />
            <TextBlock Grid.Column="1"
                       Text="Each ContentPage has its own CommandBar. It is replaced when navigating between pages."
                       FontSize="12"
                       Opacity="0.7"
                       TextWrapping="Wrap" />
          </Grid>
        </StackPanel>
      </StackPanel>
    </ScrollViewer>

    <Border DockPanel.Dock="Right" Width="1" Background="{DynamicResource SystemControlForegroundBaseMediumLowBrush}" />

    <Grid Margin="12" RowDefinitions="Auto,*">
      <TextBlock x:Name="StatusText"
                 Text="No items added"
                 FontSize="12"
                 Opacity="0.7"
                 Margin="0,0,0,8" />
      <Border Grid.Row="1"
              BorderBrush="{DynamicResource SystemControlForegroundBaseMediumLowBrush}"
              BorderThickness="1"
              CornerRadius="6"
              ClipToBounds="True">
        <NavigationPage x:Name="DemoNav" />
      </Border>
    </Grid>
  </DockPanel>
</UserControl>