DataContractJsonSerializer _json = new DataContractJsonSerializer(typeof(Person));
using (FileStream fs = File.OpenRead(@"D: empp.txt"))
{
    Person p = _json.ReadObject(fs) as Person;
    Response.Write(p.Name);//江湖小子
}

例4：
//上面大家会觉得奇怪为什么会出现k__BackingField之类的东东呢，其实是是[Serializable]造成的，我们可以用下面的方式处理
DataContractAttribute 类说明

[DataContract]
public class Person
{
   [DataMember(Order=1)]       // Order - 数据成员的序列化和反序列化的顺序
   public string Name { get; set; }
   [DataMember(Order = 2)]
   public string Address { get; set; }
   [DataMember(Order = 3)]
   public string Tel { get; set; }
}

Person _Person = new Person();
_Person.Name = "江湖小子";
_Person.Address = "北京";
_Person.Tel = "010-10000000";

DataContractJsonSerializer _json = new DataContractJsonSerializer(typeof(Person));
_json.WriteObject(Response.OutputStream, _Person);

值为：{"Name":"江湖小子","Address":"北京","Tel":"010-10000000"}

例5：

Person _Person = new Person();
_Person.Name = "江湖小子";
_Person.Address = "北京";
_Person.Tel = "010-10000000";

DataContractJsonSerializer _json = new DataContractJsonSerializer(_Person.GetType());

// 序列化
MemoryStream ms = new MemoryStream();
_json.WriteObject(ms, _Person);
ms.Position = 0;
StreamReader sr = new StreamReader(ms);
string con = sr.ReadToEnd();
Response.Write(con);//{"Name":"江湖小子","Address":"北京","Tel":"010-10000000"}

// 反序列化
byte[] buffer = System.Text.Encoding.UTF8.GetBytes(con);
MemoryStream ms2 = new MemoryStream(buffer);
Person _Person2 = _json.ReadObject(ms2) as Person;
Response.Write(_Person2.Name);//江湖小子

更好的方法：

public class Province
{
   public int Id { get; set; }
   public string Name { get; set; }
}

using System.Web.Script.Serialization;//System.Web.Extensions.dll
public static string ToJSON(object obj)
   {
       JavaScriptSerializer serializer = new JavaScriptSerializer();
       return serializer.Serialize(obj);

   }

       Province p = new Province();
       p.Id = 123;
       p.Name = "北京";
       Response.Write(ToJSON(p));//{"Id":123,"Name":"北京"}