第一种：使用JavaScriptSerializer类，适用Web平台

C#将对象序列化成JSON字符串

using System.Web.Script;
using System.Web.Script.Serialization;

            JavaScriptSerializer serializer = new JavaScriptSerializer();
            foreach (DataRow dr in dt.Rows)
            {
                Dictionary<string, string> data = http://www.mamicode.com/new Dictionary();>
输出结果为：
[{"Dev_NO":"00066666","Dev_Name":"test","Ol_Phone":"13766668888","Ol_IP":"10.196.209.174","Ol_Status":"2"},{"Dev_NO":"000F0000","Dev_Name":"test_hzlkhq","Ol_Phone":"13066668888","Ol_IP":"192.168.1.198","Ol_Status":"2"}]

如何将Json字符串转换成对象使用呢？
public class Model
    {
        public string Dev_NO { get; set; }
        public string Dev_Name { get; set; }
        public string Ol_Phone { get; set; }
        public string Ol_IP { get; set; }
        public int Ol_Status { get; set; }
    }

string requestMes="[{\"Dev_NO\":\"00066666\",\"Dev_Name\":\"test\",\"Ol_Phone\":\"13766668888\",\"Ol_IP\":\"10.196.209.174\",\"Ol_Status\":\"2\"},{\"Dev_NO\":\"000F0000\",\"Dev_Name\":\"test_hzlkhq\",\"Ol_Phone\":\"13066668888\",\"Ol_IP\":\"192.168.1.198\",\"Ol_Status\":\"2\"}]";
JavaScriptSerializer serializer = new JavaScriptSerializer();
var Json = serializer.Deserialize<List<Model>>(requestMes);
第二种使用DataContractJsonSerializer，适用通用平台

需要添加引用：System.ServiceModel.Web 和 System.Runtime.Serialization，然后使用Using：
using System.Runtime.Serialization.Json;
using System.Runtime.Serialization;

public class Model
    {
        public string Dev_NO { get; set; }
        public string Dev_Name { get; set; }
        public string Ol_Phone { get; set; }
        public string Ol_IP { get; set; }
        public int Ol_Status { get; set; }
    }

    public class Test
    {
        public static DataTable getData()
        {
            var a = "{\"Dev_NO\":\"00066666\",\"Dev_Name\":\"test\",\"Ol_Phone\":\"13766668888\",\"Ol_IP\":\"10.196.209.174\",\"Ol_Status\":\"2\"}";
            var serializer = new DataContractJsonSerializer(typeof(List<DTUModel>));
            var mStream = new MemoryStream(Encoding.UTF8.GetBytes(a.ToString()));
            List<DTUModel> list = (List<DTUModel>)serializer.ReadObject(mStream);
            DataTable dt = new DataTable();
            return dt;
        }
    }