Credit card validator

gistfile1.txt

namespace CreditCards
{
    public class CardValidation
    {
        public bool VerifyDate = true;
        public string CardName;
        public string CCNumber;
        public string CCCSV;
        public string CCName;
        public string CCExp;
        public string ErrorMessage;

        public string CCType
        {
            get {return(_CCType);}
            set {
                switch(value) {
                    case "1":
                    case "vi":
                        _CCType="vi";
                        break;
                    case "2":
                    case "mc":
                        _CCType="mc";
                        break;
                    case "3":
                    case "am":
                        _CCType="am";
                        break;
                }
            }
        } protected string _CCType="";
        public string CCTypeName
        {
            get {
                switch(CCType) {
                    case "vi":
                        return("Visa");
                    case "mc":
                        return("MasterCard");
                    case "am":
                        return("American Express");
                    default:
                        return("");
                }
            }
        }
        public int CCTypeID
        {
            get {
                switch(CCType) {
                    case "vi":
                        return(1);
                    case "mc":
                        return(2);
                    case "am":
                        return(3);
                    default:
                        return(0);
                }
            }
            set {
                CCType=value.ToString();
            }
        }

        public bool Validate() 
        {
            string CCNum;
            int CCNumberLeft;
            int CCNumberLength;
            int ShouldLength;
            string CardType="";
            int Missing;
            string YearPart;
            string MonthPart;
            bool DateValid;

            ErrorMessage="";
            //# 1) Get rid of spaces and non-numeric characters.
            CCNum = OnlyNumericSolution(CCNumber);

            //# 2) Do the first four digits fit within proper ranges?
            //#     if so, who's the card issuer and how long should the number be?
            CCNumberLeft = Convert.ToInt32(CCNum.Substring(0, 4));
            CCNumberLength = Convert.ToInt32(CCNum.Length);

                
            if (CCType == "") {
                ErrorMessage = "You must select the credit card type.";
                return(false);
            }
    

            if (CCNumberLeft >= 3000 && CCNumberLeft <= 3059) {
                CardName = "Diners Club";
                ShouldLength = 14;
            } else if (CCNumberLeft >= 3600 && CCNumberLeft <= 3699) {
                CardName = "Diners Club";
                ShouldLength = 14;
            } else if (CCNumberLeft >= 3800 && CCNumberLeft <= 3889) {
                CardName = "Diners Club";
                ShouldLength = 14;
            } else if (CCNumberLeft >= 3400 && CCNumberLeft <= 3499) {
                CardName = "American Express";
                CardType = "am";
                ShouldLength = 15;
            } else if (CCNumberLeft >= 3700 && CCNumberLeft <= 3799) {
                CardName = "American Express";
                CardType = "am";
                ShouldLength = 15;
            } else if (CCNumberLeft >= 3528 && CCNumberLeft <= 3589) {
                CardName = "JCB";
                ShouldLength = 16;
            } else if (CCNumberLeft >= 3890 && CCNumberLeft <= 3899) {
                CardName = "Carte Blache";
                ShouldLength = 14;
            } else if (CCNumberLeft >= 4000 && CCNumberLeft <= 4999) {
                CardName = "Visa";
                CardType = "vi";
                if (CCNumberLength > 14) {
                    ShouldLength = 16;
                } else if (CCNumberLength < 14) {
                    ShouldLength = 13;
                }
                else {
                    ErrorMessage = "The number entered is not a valid Visa number.";
                    return(false);
                }
            }

            else if (CCNumberLeft >= 5100 && CCNumberLeft <= 5599) {
                CardName = "MasterCard";
                CardType = "mc";
                ShouldLength = 16;
            }
            else if (CCNumberLeft == 5610) {
                CardName = "Australian BankCard";
                ShouldLength = 16;
            }
            else if (CCNumberLeft == 6011) {
                CardName = "Discover/Novus";
                ShouldLength = 16;
            } else {
                ErrorMessage = "The number entered is not valid.";
                return(false);
            }

        //'# 3) Is the number the right length?
            if (CCNumberLength != ShouldLength) {
                Missing = CCNumberLength - ShouldLength;
                if (Missing < 0)
                    ErrorMessage = "The number entered is not a valid " + CCTypeName + " number.";
                else
                    ErrorMessage = "<The number entered is not a valid " + CCTypeName + " number.";
                
                return(false);
            }


        //'# 4) Does the number pass the Mod 10 Algorithm Checksum?
            if (!((Mod10Solution(CCNum) && CCType == CardType))) {
                ErrorMessage = "The credit card number entered is not valid.";
                return(false);
            }
        
        //' Check date
            if (VerifyDate)
            {
                if (CCExp.Length != 7)
                {
                    ErrorMessage = "The date must be formatted like MM/YYYY.";
                    return (false);
                }

                YearPart = CCExp.Substring(3);
                //Mid(CCExp, 4)
                MonthPart = CCExp.Substring(0, 2);
                //Left(CCExp, 2)
                if (!(UserFunctions.IsNumeric(YearPart) && UserFunctions.IsNumeric(MonthPart)))
                {
                    ErrorMessage = "The expiration date isn't a valid date.";
                    return (false);
                }

                DateValid = true;
                if (DateTime.Now.Year > Convert.ToInt32(YearPart))
                {
                    DateValid = false;
                }
                if (DateTime.Now.Year == Convert.ToInt32(YearPart) && DateTime.Now.Month > Convert.ToInt32(MonthPart))
                {
                    DateValid = false;
                }
                if (!DateValid)
                {
                    ErrorMessage = "The expiration date has passed.";
                    return (false);
                }
            }

            return(true);
        }

        public string OnlyNumericSolution(string CCNumber) {

            string result="";
            char s;

            for (int i=0;i<CCNumber.Length;i++) {
                s=CCNumber.Substring(i,1).ToCharArray()[0];
                if (s >='0' && s<='9') {
                    result+=s;
                }
            }
            if (result.Length<13) {
                result="0000000000000";
            }
            if (result.Length > 19)
            {
                result = result.Substring(0, 19);
            }
            return(result);
        }

        private bool Mod10Solution(string CCNumber) {
            int  CCNumberLength;
            int Checksum=0;
            int Location;
            int Digit;

            CCNumberLength = CCNumber.Length;

            //'# Add even digits in even length strings
            //'# or odd digits in odd length strings.
            Location = 1 - (CCNumberLength % 2);
            while (Location <= CCNumberLength) {
                Checksum += Convert.ToInt32(CCNumber.Substring(Location, 1));
                Location += 2;
            }
            
            //'# Analyze odd digits in even length strings
            //'# or even digits in odd length strings.
            Location = (CCNumberLength % 2);
            while (Location < CCNumberLength) {
                Digit = Convert.ToInt32(CCNumber.Substring(Location, 1)) * 2;
                if (Digit < 10) {
                    Checksum += Digit;
                } else {
                    Checksum += Digit - 9;
                }
                Location += 2;
            }
            //'# Is the checksum divisible by ten?
            if (((double)Checksum / 10) == (double)Math.Truncate((double)Checksum / 10)) {
                return(true);
            } else {
                return(false);
            }

        }
    }
 
 }