在 C# 中反序列化嵌套的 .json 对象

Question

我正在尝试从 API 反序列化 C# 中的嵌套 .json (https://ergast.com/api/f1/current/results.json)，但我有点卡住了。我到处寻找解决问题的方法，但还没有发现任何有用的东西，我可能只是不明白它对我有什么帮助，考虑到我是 c# 和 API 的新手，而不是最有经验的程序员。

我在下载原始 .json 的 aspx Page_Load 中调用以下方法，稍微格式化并将其反序列化为 racesCollection。

private static RacesCollection GetRacesFromAPI(WebClient webClient)
        {
            String JSON = webClient.DownloadString("https://ergast.com/api/f1/current.json?callback=myParser&limit=1000");
            JObject data = FormatJSON(ref JSON);
            RacesCollection racesCollection = JsonConvert.DeserializeObject<RacesCollection>(data["MRData"]["RaceTable"].ToString());
            return racesCollection;
        }

..这是种族合集

    public class RacesCollection
    {
        private List<Races> races;
        public List<Races> Races { get => races; set => races = value; }
    }

..这些是我试图反序列化的类。

    public class Races
    {
        int season;
        string round;
        string url;
        string raceName;
        string date;
        string time;

        public int Season { get => season; set => season = value; }
        public string Round { get => round; set => round = value; }
        public string Url { get => url; set => url = value; }
        public string RaceName { get => raceName; set => raceName = value; }
        public string Date { get => date; set => date = value; }
        public string Time { get => time; set => time = value; }

        public Dictionary<string, Circuit> Circuit { get; set; }
        public List<Results> Results { get; set; }
    }
    public class Circuit
    {
        string circuitID;
        string circuitUrl;
        string circuitName;

        public string CircuitID { get => circuitID; set => circuitID = value; }
        public string CircuitUrl { get => circuitUrl; set => circuitUrl = value; }
        public string CircuitName { get => circuitName; set => circuitName = value; }
        public Dictionary<string, Location> Location { get; set; }
    }
    public class Results
    {
        int number;
        int position;
        int points;
        int grid;
        int laps;
        string status;
        public int Number { get => number; set => number = value; }
        public int Position { get => position; set => position = value; }
        public int Points { get => points; set => points = value; }
        public int Grid { get => grid; set => grid = value; }
        public int Laps { get => laps; set => laps = value; }
        public string Status { get => status; set => status = value; }
        public Dictionary<string, Driver> Driver { get; set; }
        public Dictionary<string, Constructor> Constructor { get; set; }
    }
    public class Driver
    {
        string driverId;
        public string DriverId { get => driverId; set => driverId = value; }
    }
    public class Constructor
    {
        string constructorId;
        public string ConstructorId { get => constructorId; set => constructorId = value; }
    }


    public class Location
    {
        float lat;
        float @long;
        string locality;
        string country;

        public float Lat { get => lat; set => lat = value; }
        public float Long { get => @long; set => @long = value; }
        public string Locality { get => locality; set => locality = value; }
        public string Country { get => country; set => country = value; }
    }

运行时，一切都正常反序列化，直到它到达 Circuit，这会引发此异常。

Newtonsoft.Json.JsonSerializationException：“将值“albert_park”转换为类型“JSONAPI.Circuit”时出错。路径 'Races[0].Circuit.circuitId'，第 10 行，位置 34。'

内部异常 ArgumentException：无法从 System.String 转换或转换为 JSONAPI.Circuit。

如果我能在这方面得到任何帮助，我们将不胜感激。

Answer 1

JSON 库会自动为您将键值对转换为类引用。 只需将public Dictionary<string, Circuit> Circuit { get; set; } 更改为public Circuit Circuit { get; set; }。

这适用于 C# 对象中的 Location、Driver 和 Constructor 字典。

Answer 2

在您提到的 json 中，电路是竞赛集合中的一个对象，而不是字典。 因此，请修改 Races 类的 Circuit 属性：

public class Races
{
    int season;
    string round;
    string url;
    string raceName;
    string date;
    string time;

    public int Season { get => season; set => season = value; }
    public string Round { get => round; set => round = value; }
    public string Url { get => url; set => url = value; }
    public string RaceName { get => raceName; set => raceName = value; }
    public string Date { get => date; set => date = value; }
    public string Time { get => time; set => time = value; }

    public Circuit Circuit { get; set; }
    public List<Results> Results { get; set; }
}

此外，在发布的 json 中，Location 属性的 lat 和 long 是字符串，而不是小数。因此，您可能还需要修改 lat 和 long 的数据类型。

附带但相关的说明，而不是使用小写的私有属性，删除私有属性并重命名公共属性以匹配您的 json 响应。如果您不想将属性重命名为驼峰式，那么您可以使用 JsonProperty 装饰每个属性（如下所示的属性 Season，但同样适用于其他属性以匹配 json）

public class Races
{
/*  
    int season;
    string round;
    string url;
    string raceName;
    string date;
    string time;
*/
    [JsonProperty("season")]
    public int Season { get; set; }
    /*
    // or use camelcasing like below then no need use JsonProperty attribute
    public int season { get; set; }
    */
    public string Round { get; set; }
    public string Url { get; set; }
    public string RaceName { get; set; }
    public string Date { get; set; }
    public string Time { get; set; }

    public Circuit Circuit { get; set; }
    public List<Results> Results { get; set; }
}

或者你可以使用 CamelCasePropertyNamesContractResolver：

var settings = new JsonSerializerSettings
{
    ContractResolver = new CamelCasePropertyNamesContractResolver()
};
RacesCollection racesCollection = JsonConvert.DeserializeObject<RacesCollection>(data["MRData"]["RaceTable"].ToString(), settings);