WDX C# Credit Card Validation Functions

• Download C# function class - 17.7 KB

Introduction

Here is my payment class for doing basic credit/debit card validation checks in C#. It includes the following functions:

• LUHN check
• Card type lookup

Background

The LUHN check was taken from another example, however I do not remember where to give credit; please let me know if you find it elsewhere so I can give credit.

The card type lookup is fairly rudimentary. It follows some simple rules as found in Wikipedia for identifying the card type. These are not exhaustive and may not always be valid as there is no defined standard, but they will give a fairly accurate lookup facility for checking against a user submitted type.

Using the code

The class contains two static methods which can be called from your routines to aid with your validation, all you need to do is pass in the card number.

LUHN check

public static bool IsLUHNValid(string ccNo)
{
    bool isValid = false;
    // will be indicator for every other number
    int indicator = 1;
    // will be used to store sum of first set of numbers
    int firstNumToAdd = 0;
    // will be used to store second set of numbers
    int secondNumToAdd = 0;
    // will be used if every other number added
    // is greater than 10, store the left-most integer here
    string num1;
    // will be used if ever yother number added
    // is greater than 10, store the right-most integer here
    string num2;

    // Convert our creditNo string to a char array
    char[] ccArr = ccNo.ToCharArray();

    if (IsNumeric(ccNo))
    {
        for (int i=ccArr.Length-1;i>=0;i--)
        {
            char ccNoAdd = ccArr[i];
            int ccAdd = Int32.Parse(ccNoAdd.ToString());
            if (indicator == 1)
            {
                // If we are on the odd number of numbers,
                // add that number to our total
                firstNumToAdd += ccAdd;
                // set our indicator to 0 so that our code
                // will know to skip to the next piece
                indicator = 0;
            }
            else
            {
                // if the current integer doubled is greater than 10
                // split the sum in to two integers and add them together
                // we then add it to our total here
                if ((ccAdd + ccAdd) >= 10)
                {
                    int temporary = (ccAdd + ccAdd);
                    num1 = temporary.ToString().Substring(0,1);
                    num2 = temporary.ToString().Substring(1,1);
                    secondNumToAdd += (Convert.ToInt32(num1) + 
                                       Convert.ToInt32(num2));
                }
                else
                {
                    // otherwise, just add them together
                    // and add them to our total
                    secondNumToAdd += ccAdd + ccAdd;
                }
                // set our indicator to 1 so for the next integer
                // we will perform a different set of code
                indicator = 1;
            }
        }
        // If the sum of our 2 numbers is divisible by 10,
        // then the card is valid. Otherwise, it is not
        if ((firstNumToAdd + secondNumToAdd) % 10 == 0)
        {
            isValid = true;
        }
        else
        {
            isValid = false;
        }
    }
    else
        isValid = false;

    return isValid;
}

Get card type

public enum CardType
{
    Invalid,
    Unknown,
    AmericanExpress,
    Bankcard,
    DinersClubInternational,
    DinersClubUSandCanada,
    DiscoverCard,
    JCB,
    Maestro,
    MasterCard,
    SoloDebit,
    SwitchDebit,
    Visa,
    VisaElectron,
    enRoute
}

public static CardType GetCardType(string strCardNumber)
{
    strCardNumber = strCardNumber.Replace(" ", "");

    // Check American Express
    if (strCardNumber.Substring(0, 2)=="34" || 
        strCardNumber.Substring(0, 2)=="37")
    {
        if (strCardNumber.Length==15)
            return CardType.AmericanExpress;
        else
            return CardType.Invalid;
    }

    // Check Bankcard
    if (strCardNumber.Substring(0, 3).ToUpper() == "DNE")
        return CardType.Bankcard;

    // Check Diners Club Internationl
    if (strCardNumber.Substring(0, 2) == "36" || 
        strCardNumber.Substring(0, 2) == "38" || 
       (Convert.ToInt32(strCardNumber.Substring(0, 3)) >= 300 && 
        Convert.ToInt32(strCardNumber.Substring(0, 3)) <= 305))

        if (strCardNumber.Length==14)
            return CardType.DinersClubInternational;
        else
            return CardType.Invalid;

    // Check Diners Club US and Canadaa
    if (strCardNumber.Substring(0, 2) == "55")
        return CardType.DinersClubUSandCanada;

    // Check Discover Card
    if (strCardNumber.Substring(0, 4) == "6011") 
        if (strCardNumber.Length==16)
            return CardType.Bankcard;
         else
            return CardType.Invalid;

    // Check JCB Card
    if (strCardNumber.Substring(0, 4) == "2131" || 
        strCardNumber.Substring(0, 4) == "1800" ) 
        if (strCardNumber.Length==15)
            return CardType.JCB;
        else
            return CardType.Invalid;

    // Check Maestro Card
    if (strCardNumber.Substring(0, 4) == "5020") 
        if (strCardNumber.Length==16)
            return CardType.Maestro;
        else
            return CardType.Invalid;

    // Check MasterCard
    if ((Convert.ToInt32(strCardNumber.Substring(0, 3)) >= 51 && 
         Convert.ToInt32(strCardNumber.Substring(0, 3)) <= 55))

        if (strCardNumber.Length==16)
            return CardType.MasterCard;
        else
            return CardType.Invalid;

    // Check Solo Card
    if (strCardNumber.Substring(0, 2) == "63" || 
        strCardNumber.Substring(0, 4) == "6767") 
        if (strCardNumber.Length==16 || strCardNumber.Length==18 ||
                                        strCardNumber.Length==19)
            return CardType.SoloDebit;
        else
            return CardType.Invalid;

    // Check Switch Card
    if (strCardNumber.Substring(0, 4) == "4903" || 
        strCardNumber.Substring(0, 4)== "4905" || 
        strCardNumber.Substring(0, 4) == "4911" || 
        strCardNumber.Substring(0, 4) == "4936" || 
        strCardNumber.Substring(0, 6) == "564182" || 
        strCardNumber.Substring(0, 6) == "633110" || 
        strCardNumber.Substring(0, 4) == "6333" || 
        strCardNumber.Substring(0, 4) == "6759") 
        if (strCardNumber.Length==16 || strCardNumber.Length==18 || 
                                        strCardNumber.Length==19)
            return CardType.SwitchDebit;
        else
            return CardType.Invalid;

    // Check Visa Electron Card
    if (strCardNumber.Substring(0, 6) == "417500") 
        if (strCardNumber.Length==16)
            return CardType.VisaElectron;
        else
            return CardType.Invalid;

    // Check Visa Card
    if (strCardNumber.Substring(0, 1) == "4") 
        if (strCardNumber.Length==16)
            return CardType.Visa;
        else
            return CardType.Invalid;

    // Check enRoute Card
    if (strCardNumber.Substring(0, 4) == "2014" || 
        strCardNumber.Substring(0, 4) == "2149") 
        if (strCardNumber.Length==15)
            return CardType.enRoute;
        else
            return CardType.Invalid;

    return CardType.Unknown;
}

History

• 1.0 - 22 August 2006 - Checks are appropriate to prefixes dictated on Wikipedia on this date.