嵌套属性不调用自定义 JsonConverter

Question

我有一个 Employee 类，其中 Manager 属性本身是 Employee 类型

public class Employee
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public Employee Manager { get; set; }
    public IList<string> Roles { get; set; }
}

我想为 Employee 类型创建一个自定义的 JsonConverter。

public class TestJsonConverter : JsonConverter
{
    public TestJsonConverter()
    {
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        JToken t = JToken.FromObject(value);
        if (t.Type != JTokenType.Object)
        {
            t.WriteTo(writer);
        }
        else
        {
            JObject o = (JObject)t;
            IList<string> propertyNames = o.Properties().Select(p => p.Name).ToList();
            o.AddFirst(new JProperty("Keys", new JArray(propertyNames)));
            o.WriteTo(writer);
        }
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        throw new NotImplementedException("Unnecessary because CanRead is false. The type will skip the converter.");
    }

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

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

ContractResolver 是

class ContractResolver : DefaultContractResolver
{
    protected override JsonObjectContract CreateObjectContract(Type objectType)
    {
        JsonObjectContract contract = base.CreateObjectContract(objectType);
        if (objectType == typeof(Employee))
        {
            contract.Converter = new TestJsonConverter();
        }
        return contract;
    }
}

当我尝试序列化 Employee 对象时，仅为顶级 Employee 对象调用自定义 JsonConverter，而不是为同样属于 Employee 类型的嵌套 Manager 属性调用：

JsonSerializerSettings settings = new JsonSerializerSettings();
settings.ContractResolver = new ContractResolver();
string json = JsonConvert.SerializeObject(employee, Formatting.Indented, settings);

Answer 1

我认为您遇到了相同的问题 Custom JsonConverter WriteJson Does Not Alter Serialization of Sub-properties:

您的转换器未应用于您的子对象的原因是因为 JToken.FromObject() 在内部使用了一个新的序列化程序实例，它不知道您的转换器。

提供的解决方案应该适合您的情况。

Answer 2

所以JsonConverter 运行一次，从根节点开始。 您将需要导航此 JSON 对象树并自行更新。

不确定这是您想要实现的目标，但我自己尝试过，您可以决定这是否适合您。

public class TestJsonConverter : JsonConverter
{
    public TestJsonConverter()
    {
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        JToken t = JToken.FromObject(value);
        if (t.Type != JTokenType.Object)
        {
            t.WriteTo(writer);
        }
        else
        {
            JObject root = (JObject)t;
            var stack = new Stack<JObject>();
            stack.Push(root);
            while (stack.Any())
            {
                var current = stack.Pop();
                var propertyNames = current.Properties().Select(p => p.Name).ToArray();
                current.AddFirst(new JProperty("Keys", new JArray(propertyNames)));

                var nestedObjects = current.Properties().Where(p => p.Value.Type == JTokenType.Object).ToArray();
                foreach (var nestedObj in nestedObjects)
                {
                    stack.Push((JObject)nestedObj.Value);
                }
            }

            root.WriteTo(writer);
        }
    }

    public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
    {
        throw new NotImplementedException("Unnecessary because CanRead is false. The type will skip the converter.");
    }

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

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