LehrerApp/LehrerApp.Desktop/App.axaml.cs

using Avalonia;
using Avalonia.Controls.ApplicationLifetimes;
using Avalonia.Markup.Xaml;
using LehrerApp.Desktop.ViewModels;
using LehrerApp.Desktop.Views;
using Microsoft.Extensions.DependencyInjection;

namespace LehrerApp.Desktop;

public class App : Application
{
    public static IServiceProvider Services { get; private set; } = null!;

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

    public override void OnFrameworkInitializationCompleted()
    {
        Services = AppBootstrapper.BuildServices();

        if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
        {
            desktop.MainWindow = new MainWindow
            {
                DataContext = Services.GetRequiredService<MainWindowViewModel>(),
            };
        }

        base.OnFrameworkInitializationCompleted();
    }
}