using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    private static readonly Dictionary<string, string> _cardStatusErrors = new Dictionary<string, string>

    {

        { "", CardStatusErrors.NotRecievedError },

        { CardStatus.NotEnrolled, CardStatusErrors.NotEnrolledError },

        { CardStatus.Undetermined, CardStatusErrors.UndeterminedEnrollmentError },

        { CardStatus.AuthenticationBypassed, CardStatusErrors.AuthenticationBypassedError }

    };

    public static void Main()

    {

        string Enrolled = null;

        var key = Enrolled ?? "";

        if(_cardStatusErrors.ContainsKey(key))

            Console.WriteLine(_cardStatusErrors[key]);

        else

            Console.WriteLine(CardStatusErrors.UnknownError);

    }

    public class CardStatus

    {

        public const string Enrolled = "Y";

        public const string NotEnrolled = "N";

        public const string Undetermined = "U";

        public const string AuthenticationBypassed = "B";

    }

    public class CardStatusErrors

    {

        public const string NotEnrolledError = "The customer’s card is not enrolled.";

        public const string UndeterminedEnrollmentError = "Unable to determine if card is enrolled.";

        public const string AuthenticationBypassedError = "Merchant rule on card authentication bypassed.";

        public const string UnknownError = "Unknown card error.";

        public const string NotRecievedError = "Customer's card status not received.";

    }

}