Question

给出这个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;

我无法使用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 setting

Answer 2

这是一种在不在json中填充$ type的方法。

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here

Answer 3

在反序列化时使用以下JsonSerializerSettings构造：

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

Answer 4

您还可以将枚举包装在一个类中：

class Wrapper
{
    IEnumerable<BaseClass> classes;
}

然后序列化并反序列化。

Answer 5

由于我只需要一个用于特定基类的一侧序列化程序（以使API返回派生类的属性），我想出了当前的解决方案

public class CustomConverter : JsonConverter<BaseClass>
{
    private readonly JsonSerializerOptions _serializerOptions;

    public CustomConverter()
    {
        _serializerOptions = new JsonSerializerOptions
        {
            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
            IgnoreNullValues = true,
        };
    }

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

    public override BaseClass Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        throw new NotImplementedException();
    }

    public override void Write(Utf8JsonWriter writer, BaseClass value, JsonSerializerOptions options)
    {
        writer.WriteStringValue(JsonSerializer.SerializeToUtf8Bytes(value, value.GetType(), _serializerOptions));
    }
}

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

5 个答案: