从苹果的iTunes类型ID服务反序列化JSON的麻烦

Question

从苹果的iTunes类型in服务返回的JSON与我在过去遇到的其他JSON不同。正因为如此，我在构建反序列化类时遇到了困难。

下面是JSON的一个示例(为了清楚起见，我已经将其删减；完整的JSON可以找到这里)：

{
    "26": {
        "name": "Podcasts",
        "id": "26",
        "url": "https://itunes.apple.com/us/genre/podcasts/id26?mt=2",
        "subgenres": {
            "1301": {
                "name": "Arts",
                "id": "1301",
                "url": "https://itunes.apple.com/us/genre/podcasts-arts/id1301?mt=2",
                "subgenres": {
                    "1306": {
                        "name": "Food",
                        "id": "1306",
                        "url": "https://itunes.apple.com/us/genre/podcasts-arts-food/id1306?mt=2"
                    },
                    "1401": {
                        "name": "Literature",
                        "id": "1401",
                        "url": "https://itunes.apple.com/us/genre/podcasts-arts-literature/id1401?mt=2"
                    },
                    "1402": {
                        "name": "Design",
                        "id": "1402",
                        "url": "https://itunes.apple.com/us/genre/podcasts-arts-design/id1402?mt=2"
                    },
                    "1405": {
                        "name": "Performing Arts",
                        "id": "1405",
                        "url": "https://itunes.apple.com/us/genre/podcasts-arts-performing-arts/id1405?mt=2"
                    },
                    "1406": {
                        "name": "Visual Arts",
                        "id": "1406",
                        "url": "https://itunes.apple.com/us/genre/podcasts-arts-visual-arts/id1406?mt=2"
                    },
                    "1459": {
                        "name": "Fashion & Beauty",
                        "id": "1459",
                        "url": "https://itunes.apple.com/us/genre/podcasts-arts-fashion-beauty/id1459?mt=2"
                    }
                }
            },
            "1321": {
                "name": "Business",
                "id": "1321",
                "url": "https://itunes.apple.com/us/genre/podcasts-business/id1321?mt=2",
                "subgenres": {
                    "1410": {
                        "name": "Careers",
                        "id": "1410",
                        "url": "https: //itunes.apple.com/us/genre/podcasts-business-careers/id1410?mt=2"
                    },
                    "1412": {
                        "name": "Investing",
                        "id": "1412",
                        "url": "https: //itunes.apple.com/us/genre/podcasts-business-investing/id1412?mt=2"
                    },
                    "1413": {
                        "name": "Management&Marketing",
                        "id": "1413",
                        "url": "https: //itunes.apple.com/us/genre/podcasts-business-management/id1413?mt=2"
                    },
                    "1471": {
                        "name": "BusinessNews",
                        "id": "1471",
                        "url": "https: //itunes.apple.com/us/genre/podcasts-business-business/id1471?mt=2"
                    },
                    "1472": {
                        "name": "Shopping",
                        "id": "1472",
                        "url": "https: //itunes.apple.com/us/genre/podcasts-business-shopping/id1472?mt=2"
                    }
                }
            }
        }
    }
}

下面是我接收数据的类：

public class PodcastGenreResult
{
    public PodcastGenreInfo GenreInfo { get; set; }
}

public class PodcastGenreInfo
{
    [JsonProperty("name")]
    public string GenreName { get; set; }
}

下面是反序列化调用：

PodcastGenreResult result = JsonConvert.DeserializeObject<PodcastGenreResult>(sResults);

其中sResults是JSON字符串。我已经确认这个字符串包含正确的数据。

在此之后，不会引发错误，但result.GenreInfo总是为null。我试过其他方法，但这是我觉得最合适的方法。大多数情况下，我使用JsonProperty属性来指定我想要的对象，但在这里我不能这样做，因为根名称会根据我所要求的ID而改变。如何定义类以反序列化数据？

Answer 1

这其实是相当普遍的。要处理键是动态的对象，需要反序列化为Dictionary<string, T>，其中T是项类。所以在你的情况下：

Dictionary<string, PodcastGenreInfo> genres = 
    JsonConvert.DeserializeObject<Dictionary<string, PodcastGenreInfo>>(sResults);

还请注意，类型对象的subgenres属性是相同的，因此您也应该将它定义为字典：

public class PodcastGenreInfo
{
    [JsonProperty("name")]
    public string GenreName { get; set; }

    [JsonProperty("subgenres")]
    public Dictionary<string, PodcastGenreInfo> Subgenres { get; set; }
}

下面是一个工作演示：

class Program
{
    static void Main(string[] args)
    {
        using (WebClient client = new WebClient())
        {
            string url = "http://itunes.apple.com/WebObjects/MZStoreServices.woa/ws/genres?id=26";
            string json = client.DownloadString(url);
            var genres = JsonConvert.DeserializeObject<Dictionary<string, PodcastGenreInfo>>(json);
            Dump(new PodcastGenreInfo { GenreName = "Genres", Subgenres = genres }, "");
        }
    }

    private static void Dump(PodcastGenreInfo genre, string indent)
    {
        Console.WriteLine(indent + genre.GenreName);
        if (genre.Subgenres != null)
            foreach (var kvp in genre.Subgenres)
                Dump(kvp.Value, indent + "  ");
    }

    public class PodcastGenreInfo
    {
        [JsonProperty("name")]
        public string GenreName { get; set; }

        [JsonProperty("subgenres")]
        public Dictionary<string, PodcastGenreInfo> Subgenres { get; set; }
    }
}

输出：

Genres
  Podcasts
    Arts
      Design
      Fashion & Beauty
      Food
      Literature
      Performing Arts
      Visual Arts
    Business
      Business News
      Careers
      Investing
      Management & Marketing
      Shopping
    Comedy
    Education
      Educational Technology
      Higher Education
      K-12
      Language Courses
      Training
    Games & Hobbies
      Automotive
      Aviation
      Hobbies
      Other Games
      Video Games
    Government & Organizations
      Local
      National
      Non-Profit
      Regional
    Health
      Alternative Health
      Fitness & Nutrition
      Self-Help
      Sexuality
    Kids & Family
    Music
    News & Politics
    Religion & Spirituality
      Buddhism
      Christianity
      Hinduism
      Islam
      Judaism
      Other
      Spirituality
    Science & Medicine
      Medicine
      Natural Sciences
      Social Sciences
    Society & Culture
      History
      Personal Journals
      Philosophy
      Places & Travel
    Sports & Recreation
      Amateur
      College & High School
      Outdoor
      Professional
    TV & Film
    Technology
      Gadgets
      Podcasting
      Software How-To
      Tech News

Answer 2

在我看来，这个问题是设计不好的json，使用的是体裁id，而不是属性名。json应该是这样的：

{"genre":{"name":"Podcasts","id":"26", ...
    "subgenres":{"genre": {"name":"Arts","id":"1301","url":

而不是：

{"26":{"name":"Podcasts","id":"26", ...
    "subgenres":{"1301":{"name":"Arts","id":"1301","url":

我会将json加载到一个动态对象中：

dynamic genres = new System.Web.Script.Serialization.JavaScriptSerializer().Deserialize<dynamic>(json);

如果需要，可以将动态对象转换为强类型对象。