直接上代碼：

            var data = new
            {
                mobile = "18888888888",
                company = "1",
                isTravel = "1",
                invoiceId = "1",
                serialId = "fd580000000f670"
            };

            var str = Newtonsoft.Json.JsonConvert.SerializeObject(data);

            
 
//動態添加memberId
            var obj = JObject.Parse(str);
            obj.Add("memberId", "123456789");

            //動態添加clientInfo，這個clientInfo下面又有一級對象
            JObject jObject = new JObject();
            jObject.Add("VersionNumber", "1.4.1");
            obj.Add("clientInfo", jObject);

            
 
var result = obj.ToString();
            Console.WriteLine(result);

參考網址：https://www.cnblogs.com/yanglang/p/6909161.html

newtonsoft動態修改JObject