http://james.newtonking.com/json/help/index.html

using Newtonsoft.Json;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

namespace AccpStudentMIS
{
    //此类目的是防治序列化Json字符串时的循环引用问题
    //此类为Object类的扩展方法，需要引用Newtonsoft.Json.dll类
    //使用方法：在Controller中调用 Content(对象.ToJsonString(), "text/html;charset=UTF-8");方法来返回Json
    public static class ObjectExtentions
    {
        public static string ToJsonString(this Object obj)
        {

JsonSerializerSettings jsSettings = new JsonSerializerSettings();
            jsSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
            return JsonConvert.SerializeObject(obj, jsSettings);
        }
    }
}

Newtonsoft中的几个妙用

/// <summary>
        /// 转化为JSON格式
        /// </summary>
        /// <param name="obj"></param>
        /// <param name="depth">RecursionLimit</param>
        /// <returns></returns>
        public static string ToJson(this object obj, int maxDepth = 10)
        {
            JsonSerializerSettings settings = new JsonSerializerSettings();
            //settings.MaxDepth = maxDepth;
            settings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
            settings.Converters.Add(new JavaScriptDateTimeConverter());
            return JsonConvert.SerializeObject(obj, settings);
        }

public static string ToJsonIsoDateTime(this object obj)
        {
            JsonSerializerSettings settings = new JsonSerializerSettings();
            settings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
            settings.Converters.Add(new IsoDateTimeConverter());
            return JsonConvert.SerializeObject(obj, settings);
        }

/// <summary>
        /// 将JSON反序列化为对象
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sJason"></param>
        /// <returns></returns>
        public static T FromJson<T>(this string obj, int maxDepth = 2)
        {
            JsonSerializerSettings settings = new JsonSerializerSettings();
            //settings.MaxDepth = maxDepth;
            settings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;
            settings.Converters.Add(new JavaScriptDateTimeConverter());
            return JsonConvert.DeserializeObject<T>(obj, settings);
        }

/// <summary>
        /// 将JSON反序列化为对象
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sJason"></param>
        /// <returns></returns>
        public static T FromJsonIsoDateTime<T>(this string obj)
        {
            return JsonConvert.DeserializeObject<T>(obj, new IsoDateTimeConverter());
        }

/// <summary>
        /// 转化为JSON格式
        /// </summary>
        /// <param name="obj"></param>
        /// <param name="depth">RecursionLimit</param>
        /// <returns></returns>
        public static string ToJson(object obj, int maxDepth = 2)
        {
            return obj.ToJson(maxDepth);
        }

/// <summary>
        /// 将JSON反序列化为对象
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sJason"></param>
        /// <returns></returns>
        public static T FromJson<T>(string obj, int maxDepth = 2)
        {
            return obj.FromJson<T>(maxDepth);
        }