人一旦觉悟，就会放弃追寻身外之物，而开始追寻内心世界的真正财富。

相关实体类:

public  class RsponseJson
    {

        [JsonProperty("msgType")]
        public string MsgType { get; set; }

        [JsonProperty("msgObj")]
        public string MsgObj { get; set; }
    }

public class MsgObjModel
    {

        [JsonProperty("sign")]
        public string Sign { get; set; }

        [JsonProperty("params")]
        public DicPara dicPara { get; set; }
    }

public  class DicPara
    {

        [JsonProperty("plateNo")]
        public string PlateNo { get; set; }

        [JsonProperty("parkIndexcode")]
        public string ParkIndexcode { get; set; }

        [JsonProperty("preFee")]
        public decimal PreFee { get; set; }

        [JsonProperty("action")]
        public string Action { get; set; }

        [JsonProperty("cloudEnterId")]
        public string CloudEnterId { get; set; }

        [JsonProperty("orderCode")]
        public string OrderCode { get; set; }

        [JsonProperty("cloudParkId")]
        public string CloudParkId { get; set; }
    }

Program.CS代码:

class Program
    {
        static void Main(string[] args)
        {
            //方法一
            string jsonstr = @"{""msgType"":""ORDER_PAY_SUCCESS"",""msgObj"":""{""sign"":""1e7068bacxxxxxxxxxxxxxxxxxxxxxxx"",""params"":{""plateNo"":""浙A99999"",""parkIndexcode"":""111"",""preFee"":100.00,""action"":""queryPreFee"",""cloudEnterId"":""111"",""orderCode"":""0719141034-6481"",""cloudParkId"":""PI1482457208756202110""}}""}";


            RsponseJson Jm = JsonConvert.DeserializeObject<RsponseJson>(jsonstr);
            MsgObjModel jmodel = JsonConvert.DeserializeObject<MsgObjModel>(Jm.MsgObj);
        }
    }

static void Main(string[] args)
        {
           //方法二，无需任何实体类
            string jsonstr = @"{""msgType"":""ORDER_PAY_SUCCESS"",""cloudParkId"":""PI1482457208756202110""}}""}";

            JObject jsonSearch = JObject.Parse(jsonstr);
            string haha = jsonSearch["msgType"].ToString();
            string  msgObjstr = jsonSearch["msgObj"].ToString();

            JObject msgObjModel= JObject.Parse(msgObjstr);
            string chepai = msgObjModel["sign"].ToString();
            string plateNo = msgObjModel["params"]["plateNo"].ToString();
        }