如何使用Newtonsoft JSON.NET将JSON反序列化为IEnumerable <BaseType>

Question

鉴于此JSON:

[
  {
    "$id": "1",
    "$type": "MyAssembly.ClassA, MyAssembly",
    "Email": "me@here.com",
  },
  {
    "$id": "2",
    "$type": "MyAssembly.ClassB, MyAssembly",
    "Email": "me@here.com",
  }
]

和这些类:

public abstract class BaseClass
{
    public string Email;
}
public class ClassA : BaseClass
{
}
public class ClassB : BaseClass
{
}

如何将JSON反序列化为:

IEnumerable<BaseClass> deserialized;

我不能使用,JsonConvert.Deserialize<IEnumerable<BaseClass>>()因为它抱怨BaseClass是抽象的.

Answer 1

你需要:

 JsonSerializerSettings settings = new JsonSerializerSettings
                 {
                     TypeNameHandling = TypeNameHandling.All
                 };

string strJson = JsonConvert.SerializeObject(instance, settings);

所以JSON看起来像这样:

{
  "$type": "System.Collections.Generic.List`1[[MyAssembly.BaseClass, MyAssembly]], mscorlib",
  "$values": [
    {
      "$id": "1",
      "$type": "MyAssembly.ClassA, MyAssembly",
      "Email": "me@here.com",
    },
    {
      "$id": "2",
      "$type": "MyAssembly.ClassB, MyAssembly",
      "Email": "me@here.com",
    }
  ]
}

然后你可以反序列化它:

BaseClass obj = JsonConvert.DeserializeObject<BaseClass>(strJson, settings)

文档:TypeNameHandling设置

Answer 2

这是一种方法,无需在json中填充$ type.

一个Json转换器:

public class FooConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return (objectType == typeof(BaseFoo));
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        JObject jo = JObject.Load(reader);
        if (jo["FooBarBuzz"].Value<string>() == "A")
            return jo.ToObject<AFoo>(serializer);

        if (jo["FooBarBuzz"].Value<string>() == "B")
            return jo.ToObject<BFoo>(serializer);

        return null;
    }

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

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }
}

使用它:

var test = JsonConvert.DeserializeObject<List<BaseFoo>>(result, new JsonSerializerSettings() 
{ 
    Converters = { new FooConverter() }
});

取自这里

Answer 3

反序列化时使用以下JsonSerializerSettings构造:

new JsonSerializerSettings()
{
    TypeNameHandling = TypeNameHandling.Objects
})