static void Main(string[] args) { Console.WriteLine("Place Orders\n"); Console.WriteLine("Please enter the User's ID: "); string userId = Console.ReadLine(); while (!Regex.IsMatch(userId, @"^[0-9]+$")) { Console.WriteLine("User ID needs to be an integer"); userId = Console.ReadLine(); } Console.WriteLine("Please enter the amount on the order: "); string amount = Console.ReadLine(); Order order = new Order() { Amount = Convert.ToDouble(amount), CustomerId = Convert.ToInt32(userId), }; OrderService service = new OrderService(); while (!service.PlaceOrder(order, Convert.ToInt32(userId))) { Console.WriteLine("Amount needs to be a number"); userId = Console.ReadLine(); } Console.WriteLine("Retrieve All Clients and their Orders\n"); foreach (Customer item in CustomerRepository.AllClients()) { Console.WriteLine("Custmer Name: " + item.Name); Console.WriteLine("Date of Birth: " + item.DateOfBirth); Console.WriteLine("Country: " + item.Country); } }