Json.NET(Newtonsoft.Json)是.Net 框架下比较流行的一款高效json序列化开源组件,支持.Net Framework 2.0 到 4.5+,并且可用于.Net各种环境Asp.net,Silverlight,Windows Phone,Windows 8等等.更多特性移步开源 性能 Json.NET 、DataContractJsonSerializer、JavascriptSeriallizer性能测试结果对比，还不错吧。
引用
方式1.下载解压引用Newtonsoft.Json.dll
方式2:Nuget安装
PM> Install-Package Newtonsoft.Json
序列化与反序列
1.基本用法，首先引用Newtonsoft.Json命名空间,定义好与json同结构的的类用于转换
Software software = new Software{ SoftID=1,
SoftName="限时免费" ,
DownloadUrl="http://itunes.apple.com/cn/app/id427577372?mt=8",
ReleaseTime=DateTime.Now
};
//序列化
string jsonStr = JsonConvert.SerializeObject(software);
//反序列化
Software objSoftware =JsonConvert.DeserializeObject(jsonStr);
Console.WriteLine(jsonStr);序列化输出
2.时间格式处理,DateTime类型序列化默认序列化如上,这种格式在其它客户端很难读取，或者想按自己的格式化
Newtonsoft.Json.Converters.IsoDateTimeConverter timeConverter = new Newtonsoft.Json.Converters.IsoDateTimeConverter();
timeConverter.DateTimeFormat = "yyyy年MM月dd日 HH:mm:ss";
Console.WriteLine(JsonConvert.SerializeObject(software, timeConverter));输出结果：
3.匿名序列化,这种方法无需事先定义与json同结构的类就能反序列化
//Json字符串
string jsonStr = @"{result:-1,desc:'参数错误，请检查格式'}";
//反序列化
var obj = JsonConvert.DeserializeAnonymousType(jsonStr, new { result = 0, desc = string.Empty });
Console.WriteLine(string.Format("result:{0} desc:{1}", obj.result, obj.desc));
4.快速定位节点，用于快速处理或者json结构较为复杂的字符串,又不想定义对应转移类,如
{"weatherinfo":{"city":"福州","city_en":"fuzhou","date_y":"2013年5月4 日","date":"","week":"星期 六","fchh":"18","cityid":"101230101","temp1":"16℃~21℃","temp2":"16℃~23℃","temp3":"17℃~24℃","temp4":"16℃~26℃","temp5":"17℃~29℃","temp6":"18℃~28℃","tempF1":"60.8℉~69.8℉","tempF2":"60.8℉~73.4℉","tempF3":"62.6℉~75.2℉","tempF4":"60.8℉~78.8℉","tempF5":"62.6℉~84.2℉","tempF6":"64.4℉~82.4℉","weather1":" 阵雨","weather2":"阵雨转阴","weather3":"阴转雷阵雨","weather4":"阵雨转雷阵 雨","weather5":"阵雨转多云","weather6":"多云转中 雨","img1":"3","img2":"99","img3":"3","img4":"2","img5":"2","img6":"4","img7":"3","img8":"4","img9":"3","img10":"1","img11":"1","img12":"8","img_single":"3","img_title1":" 阵雨","img_title2":"阵雨","img_title3":"阵雨","img_title4":"阴","img_title5":" 阴","img_title6":"雷阵雨","img_title7":"阵雨","img_title8":"雷阵 雨","img_title9":"阵雨","img_title10":"多云","img_title11":"多 云","img_title12":"中雨","img_title_single":"阵雨","wind1":"微风","wind2":"微 风","wind3":"微风","wind4":"微风","wind5":"微风","wind6":"微风","fx1":"微 风","fx2":"微风","fl1":"小于3级","fl2":"小于3级","fl3":"小于3级","fl4":"小于3 级","fl5":"小于3级","fl6":"小于3级","index":"舒适","index_d":"建议着薄型套装或牛仔衫裤等春秋过渡装。 年老体弱者宜着套装、夹克衫等。","index48":"舒适","index48_d":"建议着薄型套装或牛仔衫裤等春秋过渡装。年老体弱者宜着套 装、夹克衫等。","index_uv":"弱","index48_uv":"最弱","index_xc":"不宜","index_tr":"适 宜","index_co":"舒 适","st1":"19","st2":"14","st3":"25","st4":"14","st5":"23","st6":"16","index_cl":" 较不宜","index_ls":"不太适宜","index_ag":"易发"}}读取weatherinfo下的weather1
var obj = JObject.Parse(html);
string weather1 = (string)obj["weatherinfo"]["weather1"];