public JsonResult DeleteCustomer(Customer customer)
        {
            List<Customer> Customers = Session["Customers"] as List<Customer>;

            Customers.Remove(customer);

            HomeIndexViewModel model = new HomeIndexViewModel();
            model.Customers = Customers;

            Session["Customers"] = Customers;

            return Json(model);
        }
        public JsonResult UpdateCustomerData(Customer customer)
        {
            List<Customer> Customers = Session["Customers"] as List<Customer>;

            var _customer = (from c in Customers
                            where c.Id == customer.Id
                            select c).SingleOrDefault();

            _customer.FirstName = customer.FirstName;
            _customer.LastName = customer.LastName;
            _customer.Address = customer.Address;
            _customer.City = customer.City;

            HomeIndexViewModel model = new HomeIndexViewModel();
            model.Customers = Customers;
            model.ResultMessage = "Customer was updated successfully.";

            Session["Customers"] = Customers;

            return Json(model);
        }
        public JsonResult AddNewCustomer(Customer customer)
        {
            List<Customer> Customers = Session["Customers"] as List<Customer>;

            var _customer = (from c in Customers
                            orderby c.Id ascending
                            select c).Last();

            int _nextId = _customer.Id + 1;
            customer.Id = _nextId;
            customer.Orders = new List<Order>();

            Customers.Add(customer);

            HomeIndexViewModel model = new HomeIndexViewModel();
            model.Customers = Customers;
            model.ResultMessage = "Customer was added successfully.";

            Session["Customers"] = Customers;

            return Json(model);
        }