Avalonia/samples/ReactiveUIDemo/MainWindow.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
        x:Class="ReactiveUIDemo.MainWindow"
        xmlns:vm="using:ReactiveUIDemo.ViewModels"
        xmlns:rxui="using:Avalonia.ReactiveUI"
        Title="AvaloniaUI ReactiveUI Demo"
        x:DataType="vm:MainWindowViewModel">
  <TabControl TabStripPlacement="Left">
    <TabItem Header="RoutedViewHost">
      <DockPanel DataContext="{Binding RoutedViewHost}">
        <StackPanel DockPanel.Dock="Bottom" Orientation="Horizontal" Spacing="8">
          <Button Command="{Binding ShowFoo}">Foo</Button>
          <Button Command="{Binding ShowBar}">Bar</Button>
        </StackPanel>
        <rxui:RoutedViewHost Router="{Binding Router}"/>
      </DockPanel>
    </TabItem>
  </TabControl>
</Window>