public static T GetEntityByXml<T>(string xml, string rootNode=null) where T : new()        {            if (string.IsNullOrEmpty(xml)) return new T();            if (!string.IsNullOrEmpty(rootNode))            {                xml = string.Format("<{0}>{1}</{0}>", rootNode, xml);            }            using (TextReader reader = new StringReader(xml))            {                var serializer = new XmlSerializer(typeof(T));                return (T)serializer.Deserialize(reader);            }        }