json和对象互转，很简单的一个类。

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

using System.Runtime.Serialization.Json;
using System.ServiceModel.Web;///记得引用这个命名空间
using System.IO;

namespace TCBaseUnionPay.Business
{
    public class JsonHelper
    {
        public JsonHelper()
        {
            //
            // TODO: Add constructor logic here
            //
        }
        /// <summary>
        /// 把对象序列化 JSON 字符串 
        /// </summary>
        /// <typeparam name="T">对象类型</typeparam>
        /// <param name="obj">对象实体</param>
        /// <returns>JSON字符串</returns>
        public static string GetJson<T>(T obj)
        {
            //记住 添加引用 System.ServiceModel.Web 
            /**
             * 如果不添加上面的引用,System.Runtime.Serialization.Json; Json是出不来的哦
             * */
            DataContractJsonSerializer json = new DataContractJsonSerializer(typeof(T));
            using (MemoryStream ms = new MemoryStream())
            {
                json.WriteObject(ms, obj);
                string szJson = Encoding.UTF8.GetString(ms.ToArray());
                return szJson;
            }
        }
        /// <summary>
        /// 把JSON字符串还原为对象
        /// </summary>
        /// <typeparam name="T">对象类型</typeparam>
        /// <param name="szJson">JSON字符串</param>
        /// <returns>对象实体</returns>
        public static T ParseFormJson<T>(string szJson)
        {
            T obj = Activator.CreateInstance<T>();
            using (MemoryStream ms = new MemoryStream(Encoding.UTF8.GetBytes(szJson)))
            {
                DataContractJsonSerializer dcj = new DataContractJsonSerializer(typeof(T));
                return (T)dcj.ReadObject(ms);
            }
        }
    }
}