//在NuGet里下载安装  Newtonsoft.Json，再引用。

using Newtonsoft.Json;

//写一个用户类

public class UserDataInfo

{

    public long UserID { get; set; }

    public string UserName { get; set; }

    public string UserSex { get; set; }

    public DateTime CreateDate { get; set; }

}

//一、把用户类转成json

 UserDataInfo userDataInfo = new UserDataInfo()

 {

    UserID=,

    UserName="zhangsan",

    UserSex="male",

    CreateDate=DateTime.Now

 };

string jsonStr = JsonConvert.SerializeObject(userDataInfo);

//二、把json转成用户类

string jsonText1 = "{'UserID':'1','UserName':'zhangsan','UserSex':'male','CreateDate':'" + DateTime.Now + "'}";

string jsonText2 = "{\"UserID\":\"1\",\"UserName\":\"zhangsan\",\"UserSex\":\"male\",\"CreateDate\":\"" + DateTime.Now + "\"}";

UserDataInfo userDataInfoJson= JsonConvert.DeserializeObject<UserDataInfo>(jsonText1);