Question

我们说我有以下类结构（Building是一个抽象类）：

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，我在建筑物阵列中创建了一个带有几个平面的街道对象：

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 }
};

使用JsonConvert然后序列化对象：

var toJson = JsonConvert.SerializeObject(street);

现在我想将json转换回街道对象：

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

此操作失败，并显示以下错误：

＆＃34;无法创建Building类型的实例。 Type是接口或抽象类，无法实例化。路径＆＃39;建筑物[0] .WhichFloor＆＃39;＆＃34;

如何告诉JsonConvert类建筑物应该是一组平面？

Answer 1

根据@Evk的共享链接，您应该在序列化和反序列化时尝试将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();
    }
}

现在实现此接口

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;
        
    }
}

JsonConvert反序列化一组抽象类

2 个答案: