Demo/Program.cs

using Demo.Data.Repository;
using Demo.Domain.UseCase;
using Demo.UI;
using Microsoft.Extensions.DependencyInjection;

IServiceCollection services = new ServiceCollection();

services
    .AddSingleton<IGroupRepository, GroupRepositoryImpl>()
    .AddSingleton<IUserRepository, UserRepositoryImpl>()
    .AddSingleton<IGroupUseCase, GroupUseCase>()
    .AddSingleton<IUserUseCase, UserUseCase>()
    .AddSingleton<UserConsoleUI>()
    .AddSingleton<GroupConsoleUI>()
    .AddSingleton<MainMenuUI>();

var serviceProvider = services.BuildServiceProvider();

MainMenuUI mainMenuUI = serviceProvider.GetService<MainMenuUI>();