如何使用 json.net 在生成的 json 中“内联”属性

Question

我的一个类中有一个属性，我试图用 json.net 序列化它，我想“内联”，意思是，我不想让该属性嵌套到一个元素中属性名称，但其内容直接在其父级中。

这是一个例子，假设我有以下类结构：

public interface ISteeringWheelIdentifier {}

public interface ISteeringWheel 
{
    ISteeringWheelIdentifier Identifier {get;}
}

public class ManufacturerIdentifier : ISteeringWheelIdentifier
{
    public string ManufacturerEmail {get; set;}
}

public class PartNumberIdentifier : ISteeringWheelIdentifier
{
    public string PartNumber {get; set;}
}

public class ClassicSteeringWheel : ISteeringWheel 
{
    public ClassicSteeringWheel(ManufacturerIdentifier identifier)
    {
        Identifier = identifier;
    }

    public string HornButtonManufacturer {get; set;}

    public ISteeringWheelIdentifier Identifier {get;private set;}
}

public class ModernSteeringWheel : ISteeringWheel
{
    public ModernSteeringWheel(PartNumberIdentifier identifier)
    {
        Identifier = identifier;
    }

    public string TouchpadManufacturer {get; set;}

    public ISteeringWheelIdentifier Identifier {get;private set;}
}

public class Car 
{
    public string CarBrand {get; set;}
    public ISteeringWheel SteeringWheel {get; set;}

}

如果我尝试使用以下代码序列化两个测试对象：

public static void Main()
{
    var car1 = new Car{CarBrand="Ford", SteeringWheel = new ModernSteeringWheel(new PartNumberIdentifier{PartNumber = "123456"})};
    var json = JsonConvert.SerializeObject(car1, Formatting.Indented);
    Console.WriteLine(json);

    var car2 = new Car{CarBrand="Toyota", SteeringWheel = new ClassicSteeringWheel(new ManufacturerIdentifier{ManufacturerEmail = "test@demo.com"})};
    json = JsonConvert.SerializeObject(car2, Formatting.Indented);
    Console.WriteLine(json);
}

你会得到这个结果：

{
  "CarBrand": "Ford",
  "SteeringWheel": {
    "TouchpadManufacturer": null,
    "Identifier": {
      "PartNumber": "123456"
    }
  }
}
{
  "CarBrand": "Toyota",
  "SteeringWheel": {
    "HornButtonManufacturer": null,
    "Identifier": {
      "ManufacturerEmail": "test@demo.com"
    }
  }
}

但是，就我而言，标识符只是一种管理识别方向盘的不同方式的方法，我不需要拥有该属性。我期望的结果 Json 如下：

{
  "CarBrand": "Ford",
  "SteeringWheel": {
    "TouchpadManufacturer": null
    "PartNumber": "123456"
  }
}
{
  "CarBrand": "Toyota",
  "SteeringWheel": {
    "HornButtonManufacturer": null,
    "ManufacturerEmail": "test@demo.com"
  }
}

显然，我可以通过在 ISteeringWheel 中同时包含 ManufacturerEmail 和 PartNumber 并放置一个或另一个 null 并设置为忽略空值来做到这一点，但我宁愿将事物正确分开我的课。

我在这里用上面的代码创建了一个小提琴：https://dotnetfiddle.net/C9RPy9

Answer 1

一种方法是为 ISteeringWheelIdentifier 创建您自己的自定义 json 反序列化器，您应该在其中为每个方向盘标识符类型实现所需的反序列化结果（请参阅http://www.newtonsoft.com/json/help/html/CustomJsonConverter.htm）作为示例。然后，您应该为您的 Identifier 属性 [JsonConverter(typeof([Name of your new converter]))] 设置一个 JsonConverter 属性，它将按照您的指定进行反序列化。

编辑 - 实际实现它时，要获得所需的行为有点棘手。您需要创建的转换器是用于 ISteeringWheel 接口的转换器。在其中，遍历所有属性，直到找到标识符属性，并处理其序列化。举个例子：

    public class SteeringWheelJsonConverter : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return typeof(ISteeringWheel).IsAssignableFrom(objectType);
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        JObject jo = new JObject();
        Type type = value.GetType();

        foreach (var prop in type.GetProperties())
        {
            if (prop.CanRead)
            {
                var propVal = prop.GetValue(value, null);
                if (prop.Name == "Identifier")
                {
                    // Iterate over all properties of the identifier, but don't add the identifier object itself 
                    // to the serialized result.
                    Type identifierType = propVal.GetType();
                    foreach (var identifierProp in identifierType.GetProperties())
                    {
                        var identifierPropVal = identifierProp.GetValue(propVal, null);
                        jo.Add(identifierProp.Name, identifierPropVal != null ? JToken.FromObject(identifierPropVal, serializer) : null);
                    }
                }
                else
                {
                    // Add the property to the serialized result
                    jo.Add(prop.Name, propVal != null ? JToken.FromObject(propVal, serializer) : null);
                }
            }
        }

        jo.WriteTo(writer);
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue,
        JsonSerializer serializer)
    {
        throw new NotImplementedException();
    }

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

现在剩下的就是将属性添加到汽车类：

public class Car
{
    public string CarBrand { get; set; }

    [JsonConverter(typeof(SteeringWheelJsonConverter))]
    public ISteeringWheel SteeringWheel { get; set; }

}