.NET 6中API JSON响应反序列化问题求助

• 反序列化时触发JsonException，错误提示lat字段无法转换为FlightData类型
• 提取response字段后程序出现冻结

错误原因分析 #

1. 类型不匹配：API返回的lat、lng、alt等字段是数字类型（浮点数/整数），但FlightData类中这些属性被定义为string类型，无法直接完成转换。
2. 错误的文件读取操作：代码中使用File.ReadAllText(responseData.ToString())，此处responseData.ToString()返回的是JSON数组的文本内容，而File.ReadAllText会将该文本当作文件路径去读取，导致程序尝试访问不存在的文件，引发资源占用或无限等待，最终冻结。
3. 缺失无参数构造函数：FlightData类仅定义了带参数的构造函数，而System.Text.Json默认需要无参数构造函数才能正确实例化对象。

解决方案 #

1. 修正FlightData类的属性类型与构造函数 #

将数字类型的属性改为对应的值类型，并添加无参数构造函数：

internal class FlightData
{
    public string? hex { get; set; }
    public string? reg_number { get; set; }
    public string? flag { get; set; }
    public double? lat { get; set; }
    public double? lng { get; set; }
    public int? alt { get; set; }
    public int? dir { get; set; }
    public int? speed { get; set; }
    public double? v_speed { get; set; }
    public string? squawk { get; set; }
    public string? flight_number { get; set; }
    public string? flight_icao { get; set; }
    public string? flight_iata { get; set; }
    public string? dep_icao { get; set; }
    public string? dep_iata { get; set; }
    public string? airline_icao { get; set; }
    public string? airline_iata { get; set; }
    public string? aircraft_icao { get; set; }
    public long? updated { get; set; }
    public string? status { get; set; }

    // 添加无参数构造函数，满足反序列化要求
    public FlightData() {}

    // 保留带参数构造函数（若业务需要）
    public FlightData(string hex, string reg_number, string flag, double? lat, double? lng, int? alt, int? dir, int? speed, double? v_speed, string flight_number, string flight_icao, string flight_iata, string dep_icao, string dep_iata, string airline_icao,
        string airline_iata, string aircraft_icao, long? updated, string status)
    {
        this.hex = hex;
        this.reg_number = reg_number;
        this.flag = flag;
        this.lat = lat;
        this.lng = lng;
        this.alt = alt;
        this.dir = dir;
        this.speed = speed;
        this.v_speed = v_speed;
        this.flight_number = flight_number;
        this.flight_icao = flight_icao;
        this.flight_iata = flight_iata;
        this.dep_icao = dep_icao;
        this.dep_iata = dep_iata;
        this.airline_icao = airline_icao;
        this.airline_iata = airline_iata;
        this.aircraft_icao = aircraft_icao;
        this.updated = updated;
        this.status = status;
    }
}

2. 修正API响应处理逻辑 #

移除错误的文件读取操作，直接从JsonElement完成反序列化，同时兼容两种API响应格式：

using System.Net.Http.Headers;
using System.Text.Json;
using System.Text.Json.Serialization;
using System.Net.Http.Json;
using System.Net;

using HttpClient client = new();

await ProcessRepositoriesAsync(client);

static async Task ProcessRepositoriesAsync(HttpClient client)
{
    string apiUrl = "<<API CALL URL WITH AUTHENTICATION KEY>>";
    try
    {
        string jsonResponse = await client.GetStringAsync(apiUrl);
        var jsonDocument = JsonDocument.Parse(jsonResponse);

        List<FlightData> flightList = new();
        var deserializeOptions = new JsonSerializerOptions
        {
            PropertyNameCaseInsensitive = true, // 兼容字段大小写不匹配的情况
            IgnoreUnknownFields = true // 忽略API返回中未定义的字段（如arr_icao）
        };

        if (jsonDocument.RootElement.TryGetProperty("response", out var responseData))
        {
            // 处理含元数据的响应，直接反序列化response字段
            flightList = responseData.Deserialize<List<FlightData>>(deserializeOptions) ?? new List<FlightData>();
        }
        else
        {
            // 处理无元数据的直接数组响应
            flightList = jsonDocument.RootElement.Deserialize<List<FlightData>>(deserializeOptions) ?? new List<FlightData>();
        }

        foreach (var flight in flightList)
        {
            Console.WriteLine($"Flight Number: {flight.flight_number}, Altitude: {flight.alt}, Flag: {flight.flag}");
        }
    }
    catch (HttpRequestException ex)
    {
        Console.WriteLine($"Request Error: {ex.Message}");
    }
    catch (JsonException ex)
    {
        Console.WriteLine($"JSON Deserialization Error: {ex.Message}");
    }
}

内容的提问来源于stack exchange，提问作者Chris