自定义 JsonSerializerSettings /JsonConverter 用于不同类型的列表，每种类型都有自己的 serializerSettings

Question

我有一个需要序列化为 json 字符串的 json 根 (testRoot) 的对象列表 (resultList)。该列表包含不同类型的实例（TypeA、B、C），它们有自己的 serializerSettings。

如何实现一个自定义的 JsonConverter / JsonSerializerSettings 以便当 我调用 JsonConvert.SerializeObject(testRoot)，它应该根据该实例的设置序列化每个实例。

我无法找到解决问题的好方法。感谢您的帮助。

   class TypeA
    {
        public string Name { get; set; }
        public int intPropertyA { get; set; }
        public string strPropertyA { get; set; }
        public JsonSerializerSettings serializerSettingsA { get; set; }
    }

    class TypeB
    {
        public string Name { get; set; }
        public int intPropertyB { get; set; }
        public string strPropertyB { get; set; }
        public JsonSerializerSettings serializerSettingsB { get; set; }
    }

    class TypeC
    {
        public string Name { get; set; }
        public int intPropertyC { get; set; }
        public string strPropertyC { get; set; }
        public JsonSerializerSettings serializerSettingsC { get; set; }
    }

    static void Main(string[] args)
    {
        object[] resultList = new object[3];
        int i = 0;

        TypeA objA = new TypeA(); // assume all values initialized
        TypeB objB = new TypeB(); // assume all values initialized
        TypeC objC = new TypeC(); // assume all values initialized

        resultList[i++] = new
        {
            Name = objA.Name,
            IntValue = objA.intPropertyA,
            StringValue = objA.strPropertyA
        };

        resultList[i++] = new
        {
            Name = objB.Name,
            IntValue = objB.intPropertyB,
            StringValue = objB.strPropertyB
        };

        resultList[i++] = new
        {
            Name = objC.Name,
            IntValue = objC.intPropertyC,
            StringValue = objC.strPropertyC
        };                      

        object testRoot = new
        {
            Test = "All the test results",
            date = "",
            Results = resultList
        };

            // How to customize the JsonSerializerSettings/JsonConverter so that, while serializing each type it should use settings from that instace.
            string jsonStr = JsonConvert.SerializeObject(testRoot);

        }

    public class CompositeSerializerSettings : Newtonsoft.Json.JsonSerializerSettings
    {
        public CompositeSerializerSettings()
        {
        }
    }

    public class CompositeJsonConverter : Newtonsoft.Json.JsonConverter
    {
        public override bool CanConvert(Type objectType)
        {
            throw new NotImplementedException();
        }

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

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

Answer 1

正如我在上面的评论中指出的那样，这并不能完全回答您的问题，因为在您的测试代码中，您没有传递 TypeA 或 TypeB 或 TypeC 的实例，而是传递了从这些类派生的匿名对象。

但是，如果您实际上是在尝试序列化对象本身而不是匿名对象，并且希望序列化程序为每种类型使用自定义设置，则必须告诉它如何找到它们。

使用界面是一种选择：请注意，您必须“忽略”设置，否则它们会出现在序列化输出中 - 我设置缩进纯粹是为了表明这是有效的。

public interface ISerializerSettings
{
    JsonSerializerSettings serializerSettings { get;}
}

class TypeA : ISerializerSettings
{
    public string Name { get; set; }
    public int intPropertyA { get; set; }
    public string strPropertyA { get; set; }
    [JsonIgnore]
    public JsonSerializerSettings serializerSettings { get; } = new JsonSerializerSettings
    {
        Formatting = Formatting.Indented
    };
}

class TypeB : ISerializerSettings
{
    public string Name { get; set; }
    public int intPropertyB { get; set; }
    public string strPropertyB { get; set; }
    [JsonIgnore]
    public JsonSerializerSettings serializerSettings { get; } = new JsonSerializerSettings
    {
        Formatting = Formatting.None
    };
}

class TypeC : ISerializerSettings
{
    public string Name { get; set; }
    public int intPropertyC { get; set; }
    public string strPropertyC { get; set; }
    [JsonIgnore]
    public JsonSerializerSettings serializerSettings { get; } = new JsonSerializerSettings
    {
        Formatting = Formatting.Indented
    };
}

然后在转换器中，使用类型的设置：

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

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

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        writer.WriteRaw(JsonConvert.SerializeObject(value, ((ISerializerSettings)value).serializerSettings));
    }
}

最后，在你的程序中，告诉序列化器使用你的转换器：

string jsonStr = JsonConvert.SerializeObject(testRoot, new CompositeJsonConverter());

给定这个输入：

TypeA objA = new TypeA(); // assume all values initialized
TypeB objB = new TypeB(); // assume all values initialized
TypeC objC = new TypeC(); // assume all values initialized

object[] resultList = new object[] {
            objA, objB, objC
};

object testRoot = new
{
    Test = "All the test results",
    date = "",
    Results = resultList
};

string jsonStr = JsonConvert.SerializeObject(testRoot, new CompositeJsonConverter());

这是输出：注意 TypeB 没有格式，但其他有：

{"Test":"All the test results","date":"","Results":[{
  "Name": null,
  "intPropertyA": 0,
  "strPropertyA": null
}{"Name":null,"intPropertyB":0,"strPropertyB":null}{
  "Name": null,
  "intPropertyC": 0,
  "strPropertyC": null
}]}