Newtonsoft Json.Net 序列化 JObject 不会忽略空值,即使设置正确

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.JObjectJArray 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JValueJValue.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)JsonConvert.DeserializeObject;(jsonString)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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