public static Customer CreateCustomer(Customer.Type type, string firstname, string lastname, int userId)
        {
            if ((firstname == null) || (firstname.Trim() == ""))
                throw new ArgumentNullException("firstname");

            if ((lastname == null) || (lastname.Trim() == ""))
                throw new ArgumentNullException("lastname");

            if (userId <= 0)
                throw new ArgumentNullException("userId");

            Customer newCustomer = new Customer(type, userId);
            newCustomer.FirstName = firstname.Trim();
            newCustomer.LastName = lastname.Trim();
            newCustomer.Save(userId); // The user is creating his own record
            return newCustomer;
        }
        public static void Save(Customer customer, int actionPerformerId)
        {
            if (customer == null)
                throw new ArgumentNullException("customer");

            customer.Save(actionPerformerId);
        }