using System;
namespace prjstart
{
/* Credit card validation is
done by using Luhns formula which goes in this fashion
* Step 1: Double the
value of alternate digits of the primary account number beginning with the
second digit from the right (the first right--hand digit is the check digit.)
Step 2: Add the individual
digits comprising the products obtained in Step 1 to each of the unaffected
digits in the original number.
Step 3: The total obtained in
Step 2 must be a number ending in zero (30, 40, 50, etc.) for the account
number to be validated.
For example, to validate the
primary account number 49927398716:
Step 1:
4 9 9 2 7 3 9 8 7 1 6
x2 x2 x2
x2 x2
------------------------------
18 4 6
16 2
Step 2: 4 +(1+8)+ 9 + (4) + 7 +
(6) + 9 +(1+6) + 7 + (2) + 6
Step 3: Sum = 70 : Card number
is validated
Note: Card is valid because the
70/10 yields no remainder.
* I have implemented
the logic in C# ...Read on.........
*
*
*
*
* */
/// <summary>
/// Summary description for
Creditcardvalidation.
/// </summary>
public class
Creditcardvalidation
{
//public enum cardtype
//{
// MasterCard,Visa,AmericanExpress
//};
public string
validcardtype;
public string cardtype
{
get
{
return validcardtype;
}
set
{
validcardtype = value;
}
}
public bool validate(string crd,string
cardnumber)
{
byte[] number = new byte[16];
int len=0;
for(int i=0;i<
cardnumber.Length;i++)
{
if(char.IsDigit(cardnumber,i))
{
if(len==16)return false;
number[len++]=byte.Parse(cardnumber[i].ToString());
}
}
switch(crd)
{
case "MasterCard" :
if(len!=16)
return false;
if(number[0]!=5 || number[1]==0 || number[1] > 5)
return false;
break;
case "AmericanExpress" :
if(len!=15)
return false;
if(number[0] != 3 || (number[1] != 4 &&
number[1] != 7))
return false;
break;
case "Visa" :
if(len != 16 && len != 13)
return false;
if(number[0] != 4)
return false;
break;
}
int sum = 0;
for(int i = len - 1;
i >= 0; i--)
{
if(i % 2 == len % 2)
{
int n = number[i] * 2;
sum
+= (n / 10) + (n % 10);
}
else
sum
+= number[i];
}
if(sum == 0)
{
return false;
}
else
{
return (sum % 10 == 0);
}
}
}
}