派生类型的JSON反序列化 [英] JSON deserialization of derived types

问题描述

class Attribute1
{
}

class Attribute2 : Attribute1
{
}
class class1
{
    Attribute1 attr1;
}

class class2  : class1
{
    Attribute2 attr2;
}


var serializerSettings = new JsonSerializerSettings(){TypeNameHandling = TypeNameHandling.Objects};
class2 a = SomeValidObjectoftype Class2;
string serializedClass2 = JsonConvert.SerializeObject(a, serializerSettings);
var am =  JsonConvert.DeserializeObject<Class2>(serializedClass1);

以上所有都是JSON属性和对象.我想做的是序列化和反序列化，而不会丢失类型. 反序列化时，我丢失了am.attr2的类型.目前，它以Attribute1的形式返回.我希望它为Attribute2.那可能吗?如果是这样的话，有人可以指出我正确的做法.我加入了SerializationSettings，但仍然遇到相同的问题.

All the above are JSON properties and objects. What I am trying to do is serialize and deserialize and not lose the type. While deserializing I lose the type of am.attr2. Currently it is coming back as Attribute1. I want it as Attribute2. Is that possible? If so could someone point me to the right way of doing it. I included SerializationSettings and still hit the same issue.

推荐答案

在反序列化和序列化时，您必须通过TypeNameHandling = TypeNameHandling.Objects(或All或Auto):

You have to pass TypeNameHandling = TypeNameHandling.Objects (or All or Auto) when deserializing as well as serializing:

var am =  JsonConvert.DeserializeObject<Class2>(serializedClass1, serializerSettings );

我认为这是出于安全原因:这意味着使用默认设置在反序列化期间无法注入意外类型.从 docs :

I believe this is for security reasons: it means that an unexpected type cannot be injected during deserialization using default settings. From the docs:

TypeNameHandling在您的应用程序中应谨慎使用 从外部源反序列化JSON.传入类型应为 使用自定义 SerializationBinder 进行了验证， TypeNameHandling.None以外的值.

TypeNameHandling should be used with caution when your application deserializes JSON from an external source. Incoming types should be validated with a custom SerializationBinder when deserializing with a value other than TypeNameHandling.None.

有关此警告的必要性的讨论，请参见 Newtonsoft Json中的TypeNameHandling警告 .

For a discussion of the need for this caution see TypeNameHandling caution in Newtonsoft Json.

示例小提琴.

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