如下面的例子，很容易看出问题：

如果类本身的无参构造函数， 就添加了一些元素，那么在序列化，再反序列化，会导致元素增加。

如果要避免，必须添加：

new JsonSerializerSettings() { ObjectCreationHandling = ObjectCreationHandling.Replace }

using Newtonsoft.Json;
using System;
using System.Collections.Generic;class Program3
{static void Main(string[] args){Product product = new Product();Console.WriteLine("Orginal Count:{0}", product.ListCustomer.Count);string json = JsonConvert.SerializeObject(product);  //序列化Product result1 = JsonConvert.DeserializeObject<Product>(json);Console.WriteLine("Result Count:{0}", result1.ListCustomer.Count);Product result2 = JsonConvert.DeserializeObject<Product>(json,new JsonSerializerSettings() { ObjectCreationHandling = ObjectCreationHandling.Replace });Console.WriteLine("Result2 Count:{0}", result2.ListCustomer.Count);Console.WriteLine("--------------------------------");P2 p = new P2();p.ListCustomer = new List<int>();p.ListCustomer.AddRange(new int[]{ 1,2,3,4 });Console.WriteLine("Orginal Count:{0}", p.ListCustomer.Count);string json2 = JsonConvert.SerializeObject(p);  //序列化P2 p2Result = JsonConvert.DeserializeObject<P2>(json2);Console.WriteLine("Result Count:{0}", p2Result.ListCustomer.Count);Console.WriteLine("END");Console.Read();}public class Product{public Product(){ListCustomer = new List<int> { 1, 2, 3, 4 };}public List<int> ListCustomer { get; set; }}public class P2{public List<int> ListCustomer { get; set; }}
}