如何获得json.net序列化类从列表＆LT派生的成员; T＆GT ;? [英] How do I get json.net to serialize members of a class deriving from List<T>?

问题描述

我创建了一个类 PagedResult＆LT; T＆GT; ：列表＆LT; T＆GT; 包含了一些添加的成员，以便与我们的组件中的一个工作。然而，当我运行JSON解串器，只序列化列表。如果我用标记 [JSONObject的] 和 [JsonProperty] 那么它只会序列化的成员在派生类派生类和不列表。我如何获得这两个？

I created a class PagedResult<T> : List<T> that contains a few added members in order to work with one of our components. However, when I run json deserializer, it only serializes the list. If I markup the derived class with [JsonObject] and [JsonProperty] then it'll only serialize the members of the derived class and not the list. How do I get both?

推荐答案

在默认情况下，Json.Net将把任何类，它实现的IEnumerable 作为数组。您可以通过装饰用类[的JSONObject] 属性覆盖此行为，但随后只有对象属性将被序列化，正如你所看到的。因为它不是通过公共财产（更确切地说，它是通过的GetEnumerator（）方法暴露）暴露列表本身不会得到序列化。

By default, Json.Net will treat any class that implements IEnumerable as an array. You can override this behavior by decorating the class with a [JsonObject] attribute, but then only the object properties will get serialized, as you have seen. The list itself will not get serialized because it is not exposed via a public property (rather, it is exposed via the GetEnumerator() method).

如果你想同时，您可以做的@Konrad曾建议并在你的派生类提供的公共属性揭露列表，或者你可以写一个自定义的 JsonConverter 连载整个事情，你认为合适。后一种方法的一个例子如下：

If you want both, you can either do as @Konrad has suggested and provide a public property on your derived class to expose the list, or you can write a custom JsonConverter to serialize the whole thing as you see fit. An example of the latter approach follows.

假设你的 PagedResult＆LT; T＆GT; 类看起来是这样的：

Assuming that your PagedResult<T> class looks something like this:

class PagedResult<T> : List<T>
{
    public int PageSize { get; set; }
    public int PageIndex { get; set; }
    public int TotalItems { get; set; }
    public int TotalPages { get; set; }
}

您可以做一个转换器，它是这样的：

You can make a converter for it like this:

class PagedResultConverter<T> : JsonConverter
{
    public override bool CanConvert(Type objectType)
    {
        return (objectType == typeof(PagedResult<T>));
    }

    public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
    {
        PagedResult<T> result = (PagedResult<T>)value;
        JObject jo = new JObject();
        jo.Add("PageSize", result.PageSize);
        jo.Add("PageIndex", result.PageIndex);
        jo.Add("TotalItems", result.TotalItems);
        jo.Add("TotalPages", result.TotalPages);
        jo.Add("Items", JArray.FromObject(result.ToArray(), serializer));
        jo.WriteTo(writer);
    }

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

（另请注意， [JSONObject的] 和 [JsonProperty] 属性不是必需使用这种方法，因为什么序列化的知识被封装到转换器类。）

(Notice also that the [JsonObject] and [JsonProperty] attributes are not required with this approach, because the knowledge of what to serialize is encapsulated into the converter class.)

下面是显示在行动转换器演示：

Here is a demo showing the converter in action:

class Program
{
    static void Main(string[] args)
    {
        PagedResult<string> result = new PagedResult<string> { "foo", "bar", "baz" };
        result.PageIndex = 0;
        result.PageSize = 10;
        result.TotalItems = 3;
        result.TotalPages = 1;

        JsonSerializerSettings settings = new JsonSerializerSettings();
        settings.Converters.Add(new PagedResultConverter<string>());
        settings.Formatting = Formatting.Indented;

        string json = JsonConvert.SerializeObject(result, settings);
        Console.WriteLine(json);
    }
}

输出：

{
  "PageSize": 10,
  "PageIndex": 0,
  "TotalItems": 3,
  "TotalPages": 1,
  "Items": [
    "foo",
    "bar",
    "baz"
  ]
}

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