IsValidIP

public bool IsValidIP(string addr)
        {
            //create our match pattern
            string pattern = @"\b(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\b";
            //create our Regular Expression object
            Regex check = new Regex(pattern);
            //boolean variable to hold the status
            bool valid = false;
            //check to make sure an ip address was provided
            if (addr == "")
            {
                //no address provided so return false
                valid = false;
            }
            else
            {
                //address provided so use the IsMatch Method
                //of the Regular Expression object
                valid = check.IsMatch(addr, 0);
            }
            //return the results
            return valid;
        }