Catalog/CatalogLite/App.axaml.cs

using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Markup.Xaml;
using Microsoft.Extensions.DependencyInjection;

namespace CatalogLite;

public partial class App : Avalonia.Application
{
    public override void Initialize() => AvaloniaXamlLoader.Load(this);

    public override void OnFrameworkInitializationCompleted()
    {
        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            if (ExpirationGuard.IsExpired(out var expirationDate))
            {
                var expiredWindow = new ExpiredWindow(expirationDate);
                expiredWindow.Closed += (_, _) => desktop.Shutdown();
                desktop.MainWindow = expiredWindow;
            }
            else
            {
                desktop.MainWindow = Program.ServiceProvider.GetRequiredService<MainWindow>();
            }
        }

        base.OnFrameworkInitializationCompleted();
    }
}