使用自定义 JsonConverter 反序列化接口列表? [英] Deserializing a list of interfaces with a custom JsonConverter?

问题描述

我在 json 文件中有一个 List<ISomething>，但我找不到简单的方法不使用 TypeNameHandling.All 反序列化它(我不想/不能使用，因为 JSON 文件是手写的).

I have a List<ISomething> in a json file and I can't find an easy way to deserialize it without using TypeNameHandling.All (which I don't want / can't use because the JSON files are hand-written).

有没有办法将属性 [JsonConverter(typeof(MyConverter))] 应用于成员的列表而不是列表?

Is there a way to apply the attribute [JsonConverter(typeof(MyConverter))] to members of the list instead to the list?

{
    "Size": { "Width": 100, "Height": 50 },
    "Shapes": [
        { "Width": 10, "Height": 10 },
        { "Path": "foo.bar" },
        { "Width": 5, "Height": 2.5 },
        { "Width": 4, "Height": 3 },
    ]
}

在这种情况下，Shapes 是一个 List，其中 IShape 是与这两个实现者的接口:ShapeRect 和 ShapeDxf.

In this case, Shapes is a List<IShape> where IShape is an interface with these two implementors: ShapeRect and ShapeDxf.

我已经创建了一个 JsonConverter 子类，它将项目作为 JObject 加载，然后根据 Path 属性的存在与否检查要加载的真实类:

I've already created a JsonConverter subclass which loads the item as a JObject and then checks which real class to load given the presence or not of the property Path:

var jsonObject = JObject.Load(reader);

bool isCustom = jsonObject
    .Properties()
    .Any(x => x.Name == "Path");

IShape sh;
if(isCustom)
{
    sh = new ShapeDxf();
}
else
{
    sh = new ShapeRect();
}

serializer.Populate(jsonObject.CreateReader(), sh);
return sh;

如何将此 JsonConverter 应用于列表?

How can I apply this JsonConverter to a list?

谢谢.

推荐答案

在您的班级中，您可以使用 JsonProperty 属性并使用 ItemConverterType 参数:

In your class, you can mark your list with a JsonProperty attribute and specify your converter with the ItemConverterType parameter:

class Foo
{
    public Size Size { get; set; }

    [JsonProperty(ItemConverterType = typeof(MyConverter))]        
    public List<IShape> Shapes { get; set; }
}

或者，您可以将转换器的实例传递给 JsonConvert.DeserializeObject，假设您已实现 CanConvert 以便在 objectType == typeof 时返回 true(形状).然后 Json.Net 会将转换器应用于列表中的项目.

Alternatively, you can pass an instance of your converter to JsonConvert.DeserializeObject, assuming you have implemented CanConvert such that it returns true when objectType == typeof(IShape). Json.Net will then apply the converter to the items of the list.

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