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1. Скачиваем расширение Microsoft.Extenstions.DependencyInjection
2. пишем такой кодик

Guys i try to create di in c# with avalonia but have some problems, pls try to help me here

namespace Presence.Desktop.DI
{
    public static class ServiceCollectionExtensions
    {
        public static void AddCommonService(this IServiceCollection collection)
        {
            collection
                .AddDbContext<RemoteDatabaseContext>()
                .AddSingleton<IGroupRepository, SQLGroupRepository>()
                .AddTransient<IGroupUseCase, GroupService>()
                .AddTransient<GroupViewModel>();
        }
    }
}

И App.axaml

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

        public override void OnFrameworkInitializationCompleted()
        {
            var serviceCollection = new ServiceCollection();
            serviceCollection.AddCommonService();
            var services = serviceCollection.BuildServiceProvider();
            var mainViewModel = services.GetRequiredService<GroupViewModel>();

            if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktop)
            {
                desktop.MainWindow = new MainWindow()
                {
                    DataContext = mainViewModel,
                };
            }

            base.OnFrameworkInitializationCompleted();
        }

    }
}