ArgumentNullException system.net.dns exampple

public static IPHostEntry GetHostEntry(string hostNameOrAddress) {
            if(Logging.On)Logging.Enter(Logging.Sockets, "DNS", "GetHostEntry", hostNameOrAddress);
            //
            // demand Unrestricted DnsPermission for this call
            //
            s_DnsPermission.Demand();
 
            if (hostNameOrAddress == null) {
                throw new ArgumentNullException("hostNameOrAddress");
            }
 
            // See if it's an IP Address.
            IPAddress address;
            IPHostEntry ipHostEntry;
            if (IPAddress.TryParse(hostNameOrAddress, out address))
            {
                if (address.Equals(IPAddress.Any) || address.Equals(IPAddress.IPv6Any))
                {
                    throw new ArgumentException(SR.GetString(SR.net_invalid_ip_addr), "hostNameOrAddress");
                }
 
                ipHostEntry = InternalGetHostByAddress(address, true);
            }
            else
            {
                ipHostEntry = InternalGetHostByName(hostNameOrAddress, true);
            }
 
            if (Logging.On) Logging.Exit(Logging.Sockets, "DNS", "GetHostEntry", ipHostEntry);
            return ipHostEntry;
        }