Postal code lookup using webservice

public static class PostalLookup
    {
        public static Postal Find(string countryCode, string postalCode)
        {

            // remove letters from postal code
            postalCode = Regex.Replace(postalCode, "[^0-9]", "");

            if (string.IsNullOrEmpty(postalCode) || postalCode.Length != 4)
                return null;

            if (string.IsNullOrEmpty(countryCode))
                return null;


            // create the web request to the GeoNames interface
            const string geoNamesUrl = "http://ws.geonames.org/postalCodeLookupJSON?postalcode={0}&country={1}";
            WebRequest geoNamesRequest = WebRequest.Create(String.Format(geoNamesUrl, postalCode, countryCode));

            // make the call
            WebResponse geoNamesResponse = geoNamesRequest.GetResponse();

            // grab the response stream
            var geoNamesReader = new StreamReader(geoNamesResponse.GetResponseStream());

            // put the whole response in a string
            string geoNamesContent = geoNamesReader.ReadToEnd();

            try
            {

                JObject o = JObject.Parse(geoNamesContent);
                var postal = new Postal
                                     {
                                         Code = (string)o["postalcodes"][0]["postalcode"],
                                         PlaceName = (string)o["postalcodes"][0]["placeName"],
                                         County = (string)o["postalcodes"][0]["adminName1"]
                                     };
                return postal;
            }
            catch
            {
                return null;
            }
        }
    }

    public class Postal
    {
        public string Code { get; set; }
        public string PlaceName { get; set; }
        public string County { get; set; }
    }