Converting address to lat and lng

public void GetCoOrdinates()
        {
            string serviceUri = string.Format("http://rpc.geocoder.us/service/rest?address={0},{1},{2}", street, city, state);
            XmlDocument serviceXmlDoc = new XmlDocument();
            serviceXmlDoc.Load(serviceUri);
            XmlNamespaceManager geoCoderManager = new XmlNamespaceManager(serviceXmlDoc.NameTable);
            geoCoderManager.AddNamespace("geoCoderService", @"http://www.w3.org/2003/01/geo/wgs84_pos#");
            string longitude = serviceXmlDoc.DocumentElement.SelectSingleNode(@"//geoCoderService:long", geoCoderManager).InnerText;
            string latitude = serviceXmlDoc.DocumentElement.SelectSingleNode(@"//geoCoderService:lat", geoCoderManager).InnerText;
            MessageBox.Show(String.Format("Latitude: {0} Latitude: {1}", latitude, longitude));
        }