using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

​

        string serviceCode = "625";

        bool offlineAuth = false;

        bool deviceOnlinePin = false;

        Console.WriteLine(string.Format("Validating service code: {0}", serviceCode));

​

​

        var validator = new ServiceCodeValidator();

        var firstCharResult = validator.IsFirstDigitValid(offlineAuth, serviceCode);        

        var secondCharResult = validator.IsSecondDigitValid(offlineAuth, serviceCode);      

        var thirdCharResult = validator.IsThirdDigitValid(offlineAuth, deviceOnlinePin, serviceCode);

        if(firstCharResult || secondCharResult || thirdCharResult)

        {

            Console.WriteLine(string.Format("service code character 1 is valid: {0}", firstCharResult));

            Console.WriteLine(string.Format("service code character 2 is valid: {0}", secondCharResult));

            Console.WriteLine(string.Format("service code character 3 is valid: {0}", thirdCharResult));        

        }

        else

        {

            Console.WriteLine(string.Format("service code: {0} is valid", serviceCode));

        }

    }

}

​

​

public class ServiceCodeValidator

    {

        public bool IsFirstDigitValid(bool isOfflineeAuthorisation, string serviceCode)

        {

            return !serviceCodeSearch(isOfflineeAuthorisation, serviceCode[0], new[] { '0', '3', '4', '5', '6', '7', '8', '9' });

        }

​

        public bool IsSecondDigitValid(bool isOfflineeAuthorisation, string serviceCode)

        {

            return !serviceCodeSearch(isOfflineeAuthorisation, serviceCode[1], new[] { '1', '2', '3', '4', '5', '6', '7', '8', '9' });

        }

​

        public bool IsThirdDigitValid(bool isOfflineeAuthorisation,bool isOnlinePinVerificationAvailable, string serviceCode)

        {

            var thirdDigit = serviceCode[2];

            if (thirdDigit == '0' && !isOnlinePinVerificationAvailable)

            {

                return false;

            }

            if (serviceCodeSearch(isOfflineeAuthorisation, thirdDigit , new[] { '8', '9' }))

            {

                return false;

            }

​

            return !serviceCodeSearch(true, serviceCode[2], new[] { '3', '4', '5' });

        }

​

        private Func<bool, char, char[], bool> serviceCodeSearch = (isOffline, match, search) =>

        {

            if (!isOffline)

            {

                return false;

            }

​

            var toMatch = match;

            var found = false;

            search.ToList().ForEach(s =>

            {

                if (toMatch == s)

                {

                    found = true;

                }

            });

            return found;

        };

​

    }