//Namespace Reference
using System.Text.RegulsrExpressions

/// 

/// method to validate a credit card number
/// 

/// cc number to validate
/// true/false
public static bool validCCNum(string num)
{
    // This expression is looking for a series of numbers, which follow the pattern 
    // for Visa, MC, Discover and American Express. It also allows for dashes between sets of numbers
    string pattern = @"^((4\d{3})|(5[1-5]\d{2})|(6011))-?\d{4}-?\d{4}-?\d{4}|3[4,7][\d\s-]{15}$";
    Regex match = new Regex(pattern);
    return match.IsMatch(num);
}