}                                                   //gives the total due amount of the user for non returned item

        //ctor
        public User(AutorisationLevel level, string name, string password, double total = 0, double turnover = 0)
        {
            NonReturnedBook = 0;
            Turnover        = turnover;
            Total           = total;
            Level           = level;
            Name            = name;
            _password       = password;
        }
        //allow you to know how much user are in the collection for a determined Level
        public int UserPerLevel(AutorisationLevel autoLevel)
        {
            int _userNum = 0;

            foreach (User item in _customerList)
            {
                if (item.Level == autoLevel)
                {
                    _userNum++;
                }
            }
            return(_userNum);
        }