1、引用

using System.Web.Script.Serialization;

2、定义类

class FaceCallback
    {
        public string device_id { get; set; }
        public int pass_status { get; set; }
        public string timestamp { get; set; }
        public string user_id { get; set; }
    }

3、转换为类对象

JavaScriptSerializer js = new JavaScriptSerializer();   //实例化一个能够序列化数据的类
 FaceCallback faceCallback = js.Deserialize<FaceCallback>(content);//content为json格式数据
 string deviceId=faceCallback.device_id;