c# - 如何使用 Newtonsoft.Json 将对象序列化为带有类型信息的 json？

Question

当我序列化某些类型的对象时，我希望在 JSON 中具有类型名称的属性。我写了一个转换器：

public class TypeInfoConverter : JsonConverter {
    private readonly IEnumerable<Type> _types;

    public TypeInfoConverter(IEnumerable<Type> types) {
        Contract.Requires(types != null);

        _types = types;
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) {
        var jObject = JObject.FromObject(value, serializer);
        jObject.AddFirst(new JProperty("Type", value.GetType().Name));
        jObject.WriteTo(writer);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer) {
        return serializer.Deserialize(reader, objectType);
    }

    public override bool CanConvert(Type objectType) {
        return _types.Any(t => t.IsAssignableFrom(objectType));
    }
}

但是当我尝试序列化对象时，我在这里有一个无限递归： var jObject = JObject.FromObject(value, serializer);很明显，因为我使用了与该转换器配置的相同 JsonSerializer 实例。

如何防止使用此转换器，但我想使用为此序列化程序配置的其他转换器？

我要序列化的类型：

public interface ITaskResult {
}

public class UserHasRejectedOffer : ITaskResult {
    public string Message { get; set; }
}

public class UserHasFilledForm : ITaskResult {
    public string FormValue1 { get; set; }

    public string Formvalue2 { get; set; }
}

...

Answer 1

var jsonSerializerSettings = new JsonSerializerSettings() { 
    TypeNameHandling = TypeNameHandling.All
};
var json = JsonConvert.SerializeObject(instance, jsonSerializerSettings);

http://james.newtonking.com/json/help/index.html?topic=html/SerializationSettings.htm

Answer 2

public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer) 
    var converters = serializer.Converters.Where(x => !(x is TypeInfoConverter)).ToArray();

    var jObject = JObject.FromObject(value);
    jObject.AddFirst(new JProperty("Type", value.GetType().Name));
    jObject.WriteTo(writer, converters);
}

Answer 3

您是否尝试过创建 的新实例JsonSerializer，然后从原始序列化程序中复制所有转换器，但导致无限递归的转换器除外？

public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
{
    JsonSerializerSettings settings = new JsonSerializerSettings
    {
        Converters = serializer.Converters.Where(s => !(s is TypeInfoConverter)).ToList()
        // also copy any other custom settings from the serializer you wish to pass through
        DateFormatHandling = serializer.DateFormatHandling,
        MissingMemberHandling = serializer.MissingMemberHandling,
        NullValueHandling = serializer.NullValueHandling,
        Formatting = serializer.Formatting
    };
    var localSerializer = JsonSerializer.Create(settings);

    var jObject = JObject.FromObject(value, localSerializer);
    jObject.AddFirst(new JProperty("Type", value.GetType().Name));
    jObject.WriteTo(writer);
}