static void Main(string[] args) { Customer customer1 = new CorporateCustomer { CustomerID = 1, CustomerNumber = "12345", CompanyName = "Assistt", TaxIDNumber = "55659898965" }; Customer customer2 = new GeneralCustomer { CustomerID = 2, CustomerNumber = "12346", CustomerName = "Gizem", CustomerLastName = "Çınar" }; CustomerManager customerManager = new CustomerManager(); customerManager.Add(customer2); customerManager.Add(customer1); customerManager.Delete(customer2); customer2.CustomerNumber = "12378"; customerManager.Update(customer2); }