private static void CreateData(MyContext context)
        {
            User user = new User()
            {
                Name = "Ori"
            };

            Group group = new Group()
            {
                Name = "Friends",
                Users = new List<User>(),
            };
            context.Groups.Add(group);

            group.Users.Add(user);

            context.SaveChanges();
        }
        private static void UpdateWithSelecting(MyContext context)
        {
            UserDTO dto = new UserDTO()
            {
                id = 2,
                name = "XXX",
            };

            User user = new User()
            {
                ID = dto.id,
            };

            DbEntityEntry entry = context.Entry(user);
            entry.State = EntityState.Unchanged;

            user.Name = dto.name;

            context.SaveChanges();
        }
        private static void AddMoreData(MyContext context)
        {
            //Group group = context.Groups.Where(g => g.Name == "Friends").Single();

            Group group = (from g in context.Groups where g.Name == "Friends" select g).Single();

            User user = new User()
            {
                Name = "Roni",
            };
            group.Users.Add(user);

            context.SaveChanges();
        }