Avalonia/samples/AppWithoutLifetime/MainWindow.axaml

<Window xmlns="https://github.com/avaloniaui"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
        x:Class="AppWithoutLifetime.MainWindow"
        Title="AppWithoutLifetime">
  <StackPanel>
    <TextBlock Text="Welcome to Avalonia!"/>
    <CheckBox Content="Welcome to Avalonia!"/>
    <Button Click="Open" Content="Open"/>
  </StackPanel>
</Window>