public void EditUser(int id, User user)
        {
            List <User> users = GetAllUsers().ToList();

            users[id - 1] = user;

            JsonFileWriter.WriteToJsonUser(users, JsonFileName);
        }
        public void RemoveUser(int id)
        {
            List <User> users = GetAllUsers();

            users[id - 1]    = new User();
            users[id - 1].ID = id;

            JsonFileWriter.WriteToJsonUser(users, JsonFileName);
        }
        public void AddUser(User user)
        {
            List <User> users   = GetAllUsers();
            List <int>  userIDs = new List <int>();

            foreach (User userAlt in users)
            {
                userIDs.Add(userAlt.ID);
            }

            if (userIDs.Count != 0)
            {
                int i = userIDs.Max();
                user.ID = i + 1;
            }
            else
            {
                user.ID = 1;
            }

            users.Add(user);
            JsonFileWriter.WriteToJsonUser(users, JsonFileName);
        }