Network Programming in .NET

 // Javascript code copyright 2009 
 // This code may be used freely, as long as this copyright notice is intact.
 function Calculate(Luhn)
 {
	var sum = 0;
    for (i=0; i<luhn.length; for="" i="" (i="Luhn.length-1;" (0,1,2,3,4,-4,-3,-2,-1,0);="" array="" delta="new" var="" }="" +="parseInt(Luhn.substring(i,i+1));" sum="" {="" )="" i++="">0; i-=2 )
    {		
		var deltaIndex = parseInt(Luhn.substring(i,i+1));
		var deltaValue = delta[deltaIndex];	
		sum += deltaValue;
	}	
	var mod10 = sum % 10;
	mod10 = 10 - mod10;	
	if (mod10==10)
	{		
		mod10=0;
	}
	return mod10;
 }

 function Validate(Luhn)
 {
	var LuhnDigit = parseInt(Luhn.substring(Luhn.length-1,Luhn.length));
	var LuhnLess = Luhn.substring(0,Luhn.length-1);
	if (Calculate(LuhnLess)==parseInt(LuhnDigit))
	{
		return true;
	}	
	return false;
 }