static void Main(string[] args) { int c; bool flag = false; Customer cust = new Customer(); CustomerRepository repo = new CustomerRepository(); Console.WriteLine("Press 1 to add a customer, Press 2 to retrieve a customer, Press 3 to retrieve all customers"); do { //int.TryParse(Console.ReadLine(), out CustId); flag = int.TryParse(Console.ReadLine(), out c); if (!flag || c > 3) { Console.WriteLine("Incorrect Choice. Press 1 to add a customer, Press 2 to retrieve a customer, Press 3 to retrieve all customers"); } } while (!(flag) || c > 3); switch (c) { case 1: cust.GetDetails(); cust.dispDetails(); repo.AddCust(cust); break; case 2: repo.RetrieveCust(); break; case 3: repo.RetrieveAll(); break; default: break; } }