Замена условной логики полиморфизмом

OCP.cs

namespace CarService
{
    internal class Program
    {
        internal static void Main(string[] args)
        {
            var orderForm = new Order();

            PaymentSystem[] _paymentSystems = new[]
            {
                new PaymentSystem("QIWI"),
                new PaymentSystem("WebMoney"),
                new PaymentSystem("Card")
            };

            var paymentHandler = new PaymentHandler(_paymentSystems);

            string selectedSystemId = orderForm.ShowForm(GetPaymentSystemIds(paymentHandler));

            paymentHandler.RequestPayment(selectedSystemId);
            paymentHandler.ShowPaymentResult(selectedSystemId);
        }

        private static string[] GetPaymentSystemIds(PaymentHandler paymentHandler)
        {
            string[] availablePaymentSystemIds = { };

            foreach (PaymentSystem paymentHandlerPaymentSystem in paymentHandler.PaymentSystems)
                availablePaymentSystemIds.Append(paymentHandlerPaymentSystem.SystemId).ToArray();

            return availablePaymentSystemIds;
        }
    }

    public interface IPaymentSystem
    {
        void RequestPayment(string systemId);
        void ShowPaymentResult(string systemId);
    }

    public class Order
    {
        private string[] _paymentSystemsIds;

        public string ShowForm(string[] paymentSystemsIds)
        {
            _paymentSystemsIds = paymentSystemsIds;
            Console.WriteLine(GetNamePaymentSystem());

            //симуляция веб интерфейса
            Console.WriteLine("Какое системой вы хотите совершить оплату?");

            return Console.ReadLine();
        }

        private string GetNamePaymentSystem()
        {
            string infoPaymentSystem = "Мы принимаем: ";

            foreach (string paymentSystemsId in _paymentSystemsIds)
                infoPaymentSystem += $"{paymentSystemsId}, ";

            return infoPaymentSystem + ":";
        }
    }

    public class PaymentHandler : IPaymentSystem
    {
        private PaymentSystem[] _paymentSystems;

        public PaymentHandler(PaymentSystem[] paymentSystems) => 
            _paymentSystems = paymentSystems;

        public PaymentSystem[] PaymentSystems => 
            _paymentSystems;

        public void RequestPayment(string systemId)
        {
            _paymentSystems = _paymentSystems.Where(paymentSystem => paymentSystem.SystemId != systemId).ToArray();
            GetPaymentSystem(systemId).StartTransaction();
        }

        public void ShowPaymentResult(string systemId)
        {
            Console.WriteLine($"Вы оплатили с помощью {systemId}");
            GetPaymentSystem(systemId).FinishTransaction();
        }

        private PaymentSystem GetPaymentSystem(string systemId) =>
            _paymentSystems.First(paymentSystem => paymentSystem.SystemId == systemId);
    }

    public class PaymentSystem
    {
        private string _systemId;

        public PaymentSystem(string systemId) => 
            _systemId = systemId;

        public string SystemId => 
            _systemId;

        public void StartTransaction() => 
            Console.WriteLine($"Перевод на страницу {_systemId}...");

        public void FinishTransaction()
        {
            Console.WriteLine($"Проверка платежа через {_systemId}...");
            Console.WriteLine("Оплата прошла успешно!");
        }
    }
}