C#

abstract class CreditCard
{
    //private CreditCard(){}


    //*************************************************
    //  Input:    string representing a credit card
    //        number.
    //
    //  Returns:  true if a valid credit card number
    //            false if not
    //*************************************************
    public static bool Validate(string CreditCardNumber)
    {
        int sum = 0;

        for(int i = 0; i < CreditCardNumber.Length; i++)
        {   // odd number here
            if((int)CreditCardNumber[i]%2 != 0)
            {
                if((int)CreditCardNumber[i] * 2 > 9)
                    sum += ((int)CreditCardNumber[i] * 2) - 9;
                else
                    sum += (int)CreditCardNumber[i] * 2;
            }
            else    // even number here
            {
                if((int)CreditCardNumber[i] != 0)
                    sum += (int)CreditCardNumber[i];
            }
        }

        return(Convert.ToBoolean(sum%10));
    }

}

abstract class Poo
{
  ...
}
public class Foo : Poo
{
  Foo(){}
  ...
}

Foo f = new Foo();

public class MyAttributeAttribute : Attribute
{
    private string[] parms;
    public MyAttributeAttribute(params string[] parms)
    {
        this.parms = parms;
    }
}

[Foo("sfda","asdasd","asdasda")]
class blah {}

[Foo("sfda")]
class blaha {}