Newtonsoft Json.Net 序列化 JObject 不会忽略空值，即使设置正确-C#/.NET问题

Newtonsoft Json.Net serialize JObject doesn#39;t ignore nulls, even with the right settings(Newtonsoft Json.Net 序列化 JObject 不会忽略空值，即使设置正确)

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问题描述

我正在尝试使用 Newtonsoft Json.Net 序列化对象.

I'm trying to serialize an object using Newtonsoft Json.Net.

这个对象是一个匿名类型，里面填充了很多异构的东西，主要是常规的POCO，也有一些JObjects或者JArrays.

This object is an anonymous type filled with a lot of heterogenous things, mainly regular POCOs, but also some JObjects or JArrays.

问题是，当将 NullValueHandling 属性添加到 NullValueHandling.Ignore 时，每个 null 属性都会被忽略，但前提是它是常规".Net 对象的一部分.JObject 或 JArray 中的每个 null 属性都会保留.

The thing is that when adding the NullValueHandling property to NullValueHandling.Ignore, every null property gets ignored, but only if it's part of a "regular" .Net object. Every null property inside a JObject or JArray remains.

这是一个最小的例子:

var jobj = JObject.FromObject(new Anything{
    x = 1,
    y = "bla",
    z = null
});

var poco = new Foo {
   foo1 = "bar",
   foo2 = null
};

var serialized = JsonConvert.SerializeObject(new {
    source1 = poco,
    source2 = jobj
}, Newtonsoft.Json.Formatting.None, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore});

是否有一种简单的方法也可以忽略这些空值?我错过了一些设置选项吗?还是我必须手动处理?

Is there a simple way to ignore those null values as well ? Did I miss some setting option ? Or do I have to deal with it manually ?

推荐答案

JObject中的"null"值实际上是一个非空JValue 与 JValue.Type 等于 JTokenType.Null.当 JSON 中实际出现这样的值时，它表示 JSON 值 null.我相信它的存在是为了捕捉以下两个 JSON 对象之间的差异:


A "null" value in a JObject is actually a non-null JValue with JValue.Type equal to JTokenType.Null.  It represents a JSON value of null when such a value actually appears in the JSON.  I believe it exists to capture the difference between the following two JSON objects:
  "source2": {
    "z": null
  }

  "source2": {
  }

在第一种情况下，属性 "z" 带有 null JSON 值.在第二种情况下，属性 "z" 不存在.Linq-to-JSON 表示第一个具有空类型 JValue 的情况，而不是 JProperty.Value 实际上 为空.
In the first case, the property "z" is present with a null JSON value.  In the second case, the property "z" is not present.  Linq-to-JSON represents the first case with a null-type JValue rather than having JProperty.Value actually be null.
为防止空标记进入您的 JObject 的值，请在从某些 POCO 创建 JObject 时使用适当的序列化程序设置:
To prevent null tokens from creeping into your JObject's values, use the appropriate serializer setting when creating the JObject from some POCO:
var jobj = JObject.FromObject(new
{
    x = 1,
    y = "bla",
    z = (int?)null
}, new JsonSerializer { NullValueHandling = NullValueHandling.Ignore } );

(注意 POCO 本身不能是 JObject.无类型方法 JsonConvert.DeserializeObject(jsonString) 或 JsonConvert.DeserializeObject;(jsonString) 在 jsonString 中的根 JSON 容器是 JSON 对象时默认返回 JObject.)
(Note the POCO must not itself already be a JObject.  The untyped method(s) JsonConvert.DeserializeObject(jsonString) or JsonConvert.DeserializeObject<dynamic>(jsonString) will by default return a JObject when root JSON container in jsonString is a JSON object.)

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