public SomeEntityRepository : ISomeEntityRepository
{
   private DbContext _context;

   public SomeEntityRepository()
   {
       _context = new DbContext();
   }

   ........
}

public SomeEntityService : ISomeEntityService
{
   private ISomeEntityRepository _someEntityRepository;

   public SomeEntityService(ISomeEntityRepository someEntityRepository)
   {
       _someEntityRepository = someEntityRepository;
   }

   ........
}

public SomeEntityController : Controller
{
   private ISomeEntityService _someEntityService;

   public SomeEntityController(ISomeEntityService someEntityService)
   {
       _someEntityService = someEntityService;
   }

   ........
}