Avalonia/samples/ControlCatalog/App.xaml.cs

using Avalonia;
using Avalonia.Markup.Xaml;

namespace ControlCatalog
{
    public class App : Application
    {
        public App()
        {
            RegisterServices();
        }

        public override void Initialize()
        {
            AvaloniaXamlLoader.Load(this);
        }
    }
}