如何Json.Net没有提供空值和值区分？ [英] How to distinguish between null value and value not provided in Json.Net?

问题描述

使用Json.net反序列化是有办法，我可以在不提供IE丢失关键的空值和值区分？

Using Json.net deserialization is there a way I can distinguish between null value and value that isn't provided i.e. missing key?

我考虑这对使用部分对象更新补丁的请求，他们将代表不同的意图：

I'm considering this for partial object updates using PATCH requests and they would represent different intents:

• 空 - >设置该属性设置为null


• 缺失 - >跳过性质未提供

在JavaScript的，这是不确定的和无效的区别

In javascript this is the difference between undefined and null.

我想出了现在最好是使用 JObject 。

The best I came up with for now is to use JObject.

推荐答案

我有完全相同的问题，我无意中发现在我研究这个问题。

I had the exact same issue and I stumbled on this question during my researches.

这是普遍的共识不满意，我创建扩展可空结构，我把它叫做可设定< T>对于缺乏想象力。基本上它是一个额外的字段为空的，使用isset，这是真的无论哪个值，您存储，只要你存储的东西，只为默认为false（可设定< T>），它的别名是可设定< T&取代。 。未定义

Unsatisfied by the general consensus, I created an extended Nullable struct, which I called Settable<T> for lack of imagination. Basically it is a nullable with an additional field, IsSet, which is true no matter which value you stored, as long as you stored something, and false only for default(Settable<T>), which is aliased as Settable<T>.Undefined.

一个解串器会写的可设置< T>只有当他找到一个相应的属性，在这种情况下使用isset将为真。如果在反序列化JSON是不包括属性，默认将被保留，其具有使用isset ==假。所以，免去您的诠释？在你的DTO类型有可设置的属性是要给你不确定之间所需的差值（或者，更准确地说，未分类）和空。

A deserializer is going to write the Settable<T> only if he finds a corresponding property, in which case IsSet will be true. If the property is not included in the deserialized json, the default will be retained, which has IsSet == false. So, replacing your int? properties in your DTO type with a Settable is going to give you the required difference between undefined (or, more exactly, unspecified) and null.

耶！

我上传的实施到在Github存储库，供大家使用（没有担保，或使用您自己的风险，等等...我在医院，6根肋骨骨折和下止痛药：如果事情不工作这是你的错）：

I uploaded the implementation into a repository on Github, for everyone to use (no warranty, use at your own risk, etc... I'm in hospital with 6 broken ribs and under painkillers: if something doesn't work it's YOUR fault):

的 https://github.com/alberto-chiesa/SettableJsonProperties

编辑：
至于有关未定义序列化的注释为null ，我添加了一个自定义的ContractResolver处理可设置的属性和更新的资料库。

As for the comment about undefined serializing to null, I added a custom ContractResolver to handle Settable properties and updated the repository.

这篇关于如何Json.Net没有提供空值和值区分？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！