如何使用Json.Net和Xamarin使用SubTypes反序列化JSON? [英] How to deserialize JSON with Json.Net and Xamarin with SubTypes?

问题描述

我正在尝试反序列化此json:

I'm trying to deserialize this json:

{
  "teaser": [{
              "id": "...",
              "type": "category",
              "url": "https:...",
            },{
              "id": "...",
              "type": "brand",
              "url": "https:...",
              "videoCount": 1,
            },{
              "id": "...",
              "type": "video",
              "url": "https:...",
              "headline": "...",
            }]
}

有一个预告片列表，每个预告片根据其类型而有所不同. 这些将是我的对象:

It has a list of teasers whereby each teaser is different depending on its type. These would be my objects:

public class StartPage
{
        public IList<Teaser> Teaser { get; set; }
}

public abstract class Teaser
{
        public string Id { get; set; }
        public string Url { get; set; }
}

public class Video : Teaser
{
        public string Headline { get; set; }
}

public class Brand : Teaser
{
        public int VideoCount { get; set; }
}

我是Json.NET和Xamarin的新手，还没有找到针对这种情况的解决方案.以前，当我使用Android Studio和Gson时，可以通过以下方式注册sybtypes:

I am new to Json.NET and Xamarin and couldn't find a solution for this case yet. Before, when I was using Android Studio and Gson, I could register sybtypes the following way:

RuntimeTypeAdapterFactory<Teaser> teaserRuntimeTypeAdapterFactory = RuntimeTypeAdapterFactory.of(
                Teaser.class, "type")
                .registerSubtype(Video.class, Teaser.TYPE_VIDEO)
                .registerSubtype(Brand.class, Teaser.TYPE_BRAND)
                .registerSubtype(Category.class, Teaser.TYPE_CATEGORY);

        return new GsonBuilder()
                .registerTypeAdapterFactory(teaserRuntimeTypeAdapterFactory);

是否有类似的方法可以通过我已经忽略的Json.NET实现我想要的?

Is there a similar way to achieve what I want with Json.NET I have overlooked yet?

推荐答案

您可以做的是在代码段下面创建自定义JsonConverter并找到

What you can do is create custom JsonConverter please below snippet and find this dot net fiddle

string json ="{ 'Teaser': [{ 'id': '...', 'type': 'category', 'url': 'https:...', },{ 'id': '...', 'type': 'brand', 'url': 'https:...', 'videoCount': 1, },{ 'id': '...', 'type': 'video', 'url': 'https:...', 'headline': '...', }]}";

var list = JsonConvert.DeserializeObject<StartPage>(json);

public class BaseSpecifiedConcreteClassConverter : DefaultContractResolver
    {
        protected override JsonConverter ResolveContractConverter(Type objectType)
        {
            if (typeof(Teaser).IsAssignableFrom(objectType) && !objectType.IsAbstract)
                return null; // pretend TableSortRuleConvert is not specified (thus avoiding a stack overflow)
            return base.ResolveContractConverter(objectType);
        }
    }

public class BaseConverter : JsonConverter
    {
        static JsonSerializerSettings SpecifiedSubclassConversion = new JsonSerializerSettings() { ContractResolver = new BaseSpecifiedConcreteClassConverter() };

        public override bool CanConvert(Type objectType)
        {
            return (objectType == typeof(Teaser));
        }

        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
        {
            JObject jo = JObject.Load(reader);
            switch (jo["type"].Value<string>())
            {
                case "video":
                    return JsonConvert.DeserializeObject<Video>(jo.ToString(), SpecifiedSubclassConversion);
                case "brand":
                    return JsonConvert.DeserializeObject<Brand>(jo.ToString(), SpecifiedSubclassConversion);
                default:
                    throw new Exception();
            }
            throw new NotImplementedException();
        }

        public override bool CanWrite
        {
            get { return false; }
        }

        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
        {
            throw new NotImplementedException(); // won't be called because CanWrite returns false
        }
    }

随意在switch case硬代码类名称中创建自定义逻辑可能不是一个好主意，而是创建enum或类似的东西，但这是实现这种情况的方式

Feel free to create custom logic in switch case hard code class name might not good idea instead create enum or something like but this is how you can achieve this type of scenario

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