wcf - 为什么我的客户从 RESTFul 服务中获得了 Null 值？

Question

我根据这篇文章使用 WCF 编写了一个 RESTFul 接口。服务器端代码如下：======这是接口=======

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;
using System.ServiceModel.Web;

namespace RESTFulDaemon
{
    [ServiceContract]
    public interface IRestSerivce
    {
        //POST operation
        [OperationContract]
        [WebInvoke(UriTemplate = "", Method = "POST")]
        Person CreatePerson(Person createPerson);

        //Get Operation
        [OperationContract]
        [WebGet(UriTemplate = "")]
        List<Person> GetAllPerson();

        [OperationContract]
        [WebGet(UriTemplate = "{id}")]
        Person GetAPerson(string id);

        //PUT Operation
        [OperationContract]
        [WebInvoke(UriTemplate = "{id}", Method = "PUT")]
        Person UpdatePerson(string id, Person updatePerson);

        //DELETE Operation
        [OperationContract]
        [WebInvoke(UriTemplate = "{id}", Method = "DELETE")]
        void DeletePerson(string id);
    }
}

=======这是服务====================

using System.Collections.Generic;
using System.Linq;
using System.ServiceModel.Activation;
using System.ServiceModel;

namespace RESTFulDaemon
{
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
    [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single)]
    public class RESTService:IRestSerivce
    {
        List<Person> persons = new List<Person>();
        public Person CreatePerson(Person person)
        {
            persons.Add(person);
            return person;
        }
        public List<Person> GetAllPerson()
        {
            return persons.ToList();
        }
        public Person GetAPerson(string id)
        {
            return persons.FirstOrDefault(e => e.ID.Equals(id));
        }
        public Person UpdatePerson(string id, Person updatePerson)
        {
            Person p = persons.FirstOrDefault(e => e.ID.Equals(id));
            p.Name = updatePerson.Name;
            p.Age = updatePerson.Age;
            return p;
        }
        public void DeletePerson(string id)
        {
            persons.RemoveAll(e => e.ID.Equals(id));
        }
    }
}

=========下面是客户端代码================

private void btnCreate_Click(object sender, RoutedEventArgs e)
{
    //Client entity
    Person p = new Person();
    p.ID = "1";
    p.Name = "scy";
    p.Age = "25";
    p.Address = "China HeNan";

    HttpWebRequest request = WebRequest.Create("http://localhost:11126/RESTService/") as HttpWebRequest;
    request.KeepAlive = false;
    request.Method = "POST";

    StringWriter sw = new StringWriter();
    XmlSerializer xs = new XmlSerializer(p.GetType());
    xs.Serialize(sw,(object)p);
    string result = sw.ToString();

    //generate xml that required
    result = result.Replace("<?xml version=\"1.0\" encoding=\"utf-16\"?>\r\n",string.Empty);
    Regex regex = new Regex("<Person.*?>");
    Match m = regex.Match(result);
    if (m.Success)
    {
        result =  result.Replace(m.Value,"<Person xmlns=\"http://schemas.datacontract.org/2004/07/RESTFulDaemon\">");
    }

    byte[] buffer = Encoding.Default.GetBytes(result);
    request.ContentLength = buffer.Length;
    request.ContentType = "text/xml";
    Stream PostData = request.GetRequestStream();
    PostData.Write(buffer, 0, buffer.Length);
    PostData.Close();

    HttpWebResponse resp = request.GetResponse() as HttpWebResponse;
    StreamReader loResponseStream = new StreamReader(resp.GetResponseStream(), Encoding.Default);

    string Response = loResponseStream.ReadToEnd();
    MessageBox.Show(Response);
    loResponseStream.Close();
    resp.Close();
}

问题是：每次单击按钮时，我都会收到如下消息：

<Person xmlns="http://schemas.datacontract.org/2004/07/RESTFulDaemon">
    <ID>1</ID>
    <Name>scy</Name>
    <Age>25</Age>
    <Address>China HeNan</Address>
</Person>

但实际上我得到的结果如下：

<Person xmlns="http://schemas.datacontract.org/2004/07/RESTFulDaemon">
    <Address i:nil="true" /> 
    <Age i:nil="true" /> 
    <ID>1</ID> 
    <Name>scy</Name> 
</Person>

有人给我一些建议吗？谢谢。

编辑： 我对 RESTService 类进行了调试，发现每次调试 CreatePerson 函数时，我都会得到 Adress 和 Age 值为空的 person 实体。我认为客户端流写入可能有问题。