private static Regex isGuid = new Regex(@"^(\{){0,1}[0-9a-fA-F]{8}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{4}\-[0-9a-fA-F]{12}(\}){0,1}$");


 public static bool IsGuid(string value)
    {

        bool isValid = false;

        if (!String.IsNullOrEmpty(value))
        {
            if (isGuid.IsMatch(value))
            {
               isValid = true;
            }
        }
        return isValid;
    }