/// <summary>
        /// Check IP Address, will accept 0.0.0.0 as a valid IP
        /// </summary>
        /// <param name="strIP"></param>
        /// <returns></returns>
        public Boolean CheckIPValid(String strIP)
        {
            //  Split string by ".", check that array length is 3
            char chrFullStop = '.';
            string[] arrOctets = strIP.Split(chrFullStop);
            if (arrOctets.Length != 4)
            {
                return false;
            }
            //  Check each substring checking that the int value is less than 255 and that is char[] length is !> 2
            Int16 MAXVALUE = 255;
            Int32 temp; // Parse returns Int32
            foreach (String strOctet in arrOctets)
            {
                if (strOctet.Length > 3)
                {
                    return false;
                }

                temp = int.Parse(strOctet);
                if (temp > MAXVALUE)
                {
                    return false;
                }
            }
            return true;
        }

Quick method to validate a string is a valid IP address.

Validating an IP String in C#

ip, c#

C#