c＃使用JSON.NET继承私有字段进行序列化

我有一个像这样的对象结构（在外部dll中）：

    public class Demo2 { 
        private int count;
        public Demo2() { 
            count = 2;
        }
    }
    public class MyDemo : Demo2  {
        private int count;
        public MyDemo() { 
            count = 3;
        }
    }
    public class Perform    {
        static void Main(string[] args)    {
            MyDemo d = new MyDemo();

            String json = JsonSerializer.SerializeOnce(d);
            Console.WriteLine(json);
            /* print: {count: 3} */
        }
    }

我需要这个：“{count：3，base：{count：2}}”。 稍后反序列化

---

假设你的对象结构（在外部DLL中）不能以任何方式修改，你仍然可以通过使用自定义的JsonConverter来创建你需要的JSON，这个JsonConverter在内部使用一个定制的ContractResolver来生成每个级别的公共和专用字段列表具有关联的get和set方法的类型层次结构：

public class DeclaredFieldJsonConverter<T> : JsonConverter where T: new()
{
    const string basePropertyName = "base";

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

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        if (reader.TokenType == JsonToken.Null)
            return null;

        var jObj = JObject.Load(reader);

        existingValue = existingValue ?? new T();
        var type = existingValue.GetType();

        while (jObj != null && type != null)
        {
            var basejObj = jObj.ExtractPropertyValue(basePropertyName) as JObject;
            JsonObjectContract contract = (JsonObjectContract)DeclaredFieldContractResolver.Instance.ResolveContract(type);
            foreach (var jProperty in jObj.Properties())
            {
                var property = contract.Properties.GetClosestMatchProperty(jProperty.Name);
                if (property == null)
                    continue;
                var value = jProperty.Value.ToObject(property.PropertyType, serializer);
                property.ValueProvider.SetValue(existingValue, value);
            }
            type = type.BaseType;
            jObj = basejObj;
        }

        return existingValue;
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        WriteJson(writer, value, value.GetType(), serializer);
    }

    void WriteJson(JsonWriter writer, object value, Type type, JsonSerializer serializer)
    {
        JsonObjectContract contract = (JsonObjectContract)DeclaredFieldContractResolver.Instance.ResolveContract(type);

        writer.WriteStartObject();
        foreach (var property in contract.Properties.Where(p => !p.Ignored))
        {
            writer.WritePropertyName(property.PropertyName);
            serializer.Serialize(writer, property.ValueProvider.GetValue(value));
        }

        var baseType = type.BaseType;
        if (baseType != null && baseType != typeof(object))
        {
            writer.WritePropertyName(basePropertyName);
            WriteJson(writer, value, baseType, serializer);
        }

        writer.WriteEndObject();
    }
}

public static class JsonExtensions
{
    public static JToken ExtractPropertyValue(this JObject obj, string name)
    {
        if (obj == null)
            return null;
        var property = obj.Property(name);
        if (property == null)
            return null;
        var value = property.Value;
        property.Remove();
        property.Value = null;
        return value;
    }
}

class DeclaredFieldContractResolver : DefaultContractResolver
{
    // As of 7.0.1, Json.NET suggests using a static instance for "stateless" contract resolvers, for performance reasons.
    // http://www.newtonsoft.com/json/help/html/ContractResolver.htm
    // http://www.newtonsoft.com/json/help/html/M_Newtonsoft_Json_Serialization_DefaultContractResolver__ctor_1.htm
    // "Use the parameterless constructor and cache instances of the contract resolver within your application for optimal performance."
    // See also https://stackoverflow.com/questions/33557737/does-json-net-cache-types-serialization-information
    static DeclaredFieldContractResolver instance;

    // Explicit static constructor to tell C# compiler not to mark type as beforefieldinit
    static DeclaredFieldContractResolver() { instance = new DeclaredFieldContractResolver(); }

    public static DeclaredFieldContractResolver Instance { get { return instance; } }

    protected override List<MemberInfo> GetSerializableMembers(Type objectType)
    {
        var fields = objectType.GetFields(BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.DeclaredOnly).Where(f => !f.IsNotSerialized);
        return fields.Cast<MemberInfo>().ToList();
    }

    protected override JsonObjectContract CreateObjectContract(Type objectType)
    {
        var contract = base.CreateObjectContract(objectType);
        contract.MemberSerialization = MemberSerialization.Fields;
        return contract;
    }

    protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
    {
        return base.CreateProperties(type, MemberSerialization.Fields);
    }
}

然后使用它如下：

var demo = new MyDemo();
var json = JsonConvert.SerializeObject(demo, new DeclaredFieldJsonConverter<MyDemo>());

样品小提琴。

请注意，如果在类型层次结构中存在名为base的字段，则会写入重复的JSON属性名称，导致反序列化时可能会丢失信息。 您可能需要检查并以某种方式处理它。

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