JsonConvert 反序列化抽象数组类

Question

假设我有以下 class 结构（建筑是抽象的 class）：

public class Street
{
    public string StreetName { get; set; }

    public Building[] Buildings { get; set; }
}

public abstract class Building
{
    public string Name { get; set; }
}

public class House : Building
{
    public int Floors { get; set; }
}

public class Flat : Building
{
    public int WhichFloor { get; set; }
}

然后我在建筑物数组中创建一个街道对象，其中包含一些公寓：

Flat f1 = new Flat { Name = "Flat 1", WhichFloor = 1 };
Flat f2 = new Flat { Name = "Flat 2", WhichFloor = 2 };

Street street = new Street
{
    StreetName = "Street Name",
    Buildings = new[] { f1, f2 }
};

然后使用 JsonConvert 序列化对象：

var toJson = JsonConvert.SerializeObject(street);

现在我想将 json 转换回街道对象：

var fromJson = JsonConvert.DeserializeObject<Street>(toJson);

失败并出现以下错误：

"Could not create an instance of type Building. Type is an interface or abstract class and cannot be instantiated. Path 'Buildings[0].WhichFloor'"

我如何告诉 JsonConvert class 建筑物应该是一组公寓？

Answer 1

根据@Evk 的分享 link，您应该尝试在序列化和反序列化时将 TypeNameHandling 设置为 TypeNameHandling.Auto：

var toJson = JsonConvert.SerializeObject(street, Newtonsoft.Json.Formatting.Indented, new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.Auto
});


var fromJson = JsonConvert.DeserializeObject<Street>(toJson, new JsonSerializerSettings
{
    TypeNameHandling = TypeNameHandling.Auto
});

Answer 2

public abstract class JsonCreationConverter<T> : JsonConverter
{
    protected abstract T Create(Type objectType, JObject jObject);

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

    public override object ReadJson(JsonReader reader,Type objectType,
        object existingValue, JsonSerializer serializer)
    {
        try
        {
            var jObject = JObject.Load(reader);
            var target = Create(objectType, jObject);
            serializer.Populate(jObject.CreateReader(), target);
            return target;
        }
        catch (JsonReaderException)
        {
            return null;
        }
    }

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

现在实现这个接口

public class SportActivityConverter : JsonCreationConverter<BaseSportActivity>
{
    protected override BaseSportActivity Create(Type objectType, JObject jObject)
    {
        BaseSportActivity result = null;
        try
        {
            switch ((ESportActivityType)jObject["activityType"].Value<int>())
            {
                case ESportActivityType.Football:
                    result = jObject.ToObject<FootballActivity>();
                    break;

                case ESportActivityType.Basketball:
                    result = jObject.ToObject<BasketballActivity>();
                    break;
            }
            
        }
        catch(Exception ex)
        {
            Debug.WriteLine(ex);
        }

        return result;
        
    }
}

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