[XmlIgnore]

        public DateTime ApplicationDatetime { get; set; }

        [XmlElement("ApplicationDatetime")]

        public string ApplicationDatetimeString

        {

            get { return ApplicationDatetime.ToString("yyyy-MM-dd HH:mm:ss"); }

            set { ApplicationDatetime = DateTime.Parse(value); }

        }

        static public string SerializeToXml<T>(T obj)

        {

            string xmlString = string.Empty;

            //XmlSerializer xmlSerializer = new XmlSerializer(typeof(T));

            //using (MemoryStream ms = new MemoryStream())

            //{

            //    xmlSerializer.Serialize(ms, obj);

            //    xmlString = Encoding.UTF8.GetString(ms.ToArray());

            //}

            Encoding encoding = Encoding.UTF8;

            using (MemoryStream memoryStream = new MemoryStream())

            {

                XmlSerializer xmlSerializer = new XmlSerializer(obj.GetType());

                XmlSerializerNamespaces namespaces = new XmlSerializerNamespaces();

                namespaces.Add("", "");

                XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream, encoding);

                xmlTextWriter.Formatting = Formatting.None;

                xmlSerializer.Serialize(xmlTextWriter, obj, namespaces);

                xmlTextWriter.Flush();

                xmlTextWriter.Close();

                xmlString = encoding.GetString(memoryStream.ToArray());

            }

            return xmlString;

        }

            string queryParameters = WebUtils.SerializeToXml(posQueryParameters);

<Entity><EntityName>我和coffee</EntityName><PId></PId><LoanId>c70215bbc6dd4722b51d2bb93c1a81bd</LoanId><BankCardNo /><MobilePhone /><CheckEmployee>dkx4003</CheckEmployee><ApplicationDatetime>-- ::</ApplicationDatetime><Role>PR</Role></Entity>