Json.net反序列化的列表给出了重复项 [英] Json.net deserializing list gives duplicate items

问题描述

我刚开始使用Newtonsoft.Json（Json.net）。在我的第一个简单的测试，我反序列化泛型列表时遇到了一个问题。在我的代码示例如下序列化对象，包含三种类型的简单的整数列表（财产，成员var和数组）的。

I have just started using Newtonsoft.Json (Json.net). In my first simple test, I ran into a problem when deserializing generic lists. In my code sample below I serialize an object, containing three types of simple integer lists (property, member var and array).

生成的JSON看起来很好（的名单转换成JSON阵列）。然而，当我反序列化JSON回同一类型的一个新对象，所有列表项被复制，期望的阵列。我已经说明，通过序列化它第二次。

The resulting json looks fine (the lists are converted into json-arrays). However, when I deserialize the json back to a new object of the same type, all list items are duplicated, expect for the array. I've illustrated that by serializing it a second time.

大约从搜索，我读过，有可能是一个私人支持字段的列出了。解串器也就罢了

From searching around, I've read that there may be a "private" backing field to the lists that the deserializer also fills.

所以我的问题是：是否有一个（最好是简单的）方式，以避免在下列情况下，重复项目

So my question is: Is there a (preferably simple) way to avoid duplicate items in following case?

using System;
using System.Collections.Generic;
using Newtonsoft.Json;

namespace JsonSerializeExample
{
    public class Program
    {
        static void Main()
        {
            var data = new SomeData();
            var json = JsonConvert.SerializeObject(data);
            Console.WriteLine("First : {0}", json);
            var data2 = JsonConvert.DeserializeObject<SomeData>(json);
            var json2 = JsonConvert.SerializeObject(data2);
            Console.WriteLine("Second: {0}", json2);
        }
    }

    public class SomeData
    {
        public string SimpleField;
        public int[] IntArray;
        public IList<int> IntListProperty { get; set; }
        public IList<int> IntListMember;

        public SomeData()
        {
            SimpleField = "Some data";
            IntArray = new[] { 7, 8, 9 };
            IntListProperty = new List<int> { 1, 2, 3 };
            IntListMember = new List<int> { 4, 5, 6 };
        }
    }
}

结果输出

Resulting output

First : {"SimpleField":"Some data","IntArray":[7,8,9],"IntListMember":[4,5,6],"IntListProperty":[1,2,3]}
Second: {"SimpleField":"Some data","IntArray":[7,8,9],"IntListMember":[4,5,6,4,5,6],"IntListProperty":[1,2,3,1,2,3]}

有可能会出现一些与的 Json.Net复制私人列表项。不过，我觉得我的问题就更简单了，而我还没有想通了。

There may be some overlap here with Json.Net duplicates private list items. However, I think my problem is even simpler, and I still haven't figured it out.

推荐答案

这是因为你添加在构造函数项。在解串器处理列表时，通常的做法基本上是：

That is because you are adding items in the constructor. A common approach in deserializers when processing a list is basically:

• 通过吸气
  读取列表
  
  
  • 如果该列表为空：创建一个新的列表，并通过属性setter分配，如果一个
  
  

  这是因为大多数列表成员没有setter方法，即

  this is because most list members don't have setters, i.e.

  public List<Foo> Items {get {...}} // <=== no set
  

  
  
  

  与数组不同，它必须有一个设置器，是有用的;因此，这种方法通常是：

  Contrast to arrays, which must have a setter to be useful; hence the approach is usually:

  
  
  • 反序列化反过来每个项目，追加（添加）到一个临时目录
  
  
  • 列表转换为数组（的ToArray ），并通过二传分配
  
  
  • deserialize each item in turn, and append (Add) to a temporary list
  • convert the list to an array (ToArray), and assign via the setter

  有些串行给你选项来控制这种行为（别人不一样）;有的串行给你完全绕过构造（别人不一样）的能力。

  Some serializers give you options to control this behavior (others don't); and some serializers give you the ability to bypass the constructor completely (others don't).

  这篇关于Json.net反序列化的列表给出了重复项的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！