NebulaLauncher/Nebula.UpdateResolver/App.axaml.cs

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

namespace Nebula.UpdateResolver;

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

    public override void OnFrameworkInitializationCompleted()
    {
        var services = new ServiceCollection();
        services.AddServices();
        services.AddTransient<MainWindow>();

        var serviceProvider = services.BuildServiceProvider();
        
        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            desktop.MainWindow = serviceProvider.GetService<MainWindow>();
        }

        base.OnFrameworkInitializationCompleted();
    }
}