如何将API返回的JSON正确反序列化为自定义C#对象

你当前的C#调用API代码：

using (HttpResponseMessage response = client.GetAsync(postMethod.ToString()).Result)
{
    if (response.IsSuccessStatusCode)
    {
        var Json = response.Content.ReadAsStringAsync().Result;
        Console.WriteLine(Json);

        var y = JsonSerializer.Deserialize<PersonInfoJson>(Json);
        Console.Write("r= " + y.requester); 
        Console.Write("id= " + y.id);
    }
}

API返回的JSON结构：

{"requesters":[{"active":true,"address":null,"background_information":null,"can_see_all_changes_from_associated_departments":false,"can_see_all_tickets_from_associated_departments":false,"created_at":"2022-12-15T21:07:22Z","custom_fields":{"blah_id":"00002342"},"department_ids":[1111111],"department_names":["Student"],"external_id":null,"first_name":"mike","has_logged_in":false,"id":123456,"is_agent":false,"job_title":null,"language":"en","last_name":"ishere","location_id":null,"location_name":null,"mobile_phone_number":"111-111-1111","primary_email":"email@email.com","reporting_manager_id":null,"secondary_emails":["anotheremail@email.com"],"time_format":"12h","time_zone":"Eastern Time (US & Canada)","updated_at":"2023-02-03T16:59:41Z","vip_user":false,"work_phone_number":"222-222-2222"}]}

你定义的PersonInfoJson类：

public partial class PersonInfoJson
{
    public string requester { get; set; }
    public string department_names { get; set; }
    public string first_name { get; set; }
    public string job_title { get; set; }

    public string last_name { get; set; }
    public string mobile_phone_number { get; set; }
    public string primary_email { get; set; }
    public string secondary_emails { get; set; }
    public string work_phone_number { get; set; }
    public DateTime updated_at { get; set; }
    public int id { get; set; }
}

执行反序列化后，整个JSON被存入y.requester字段，无法正确映射requesters数组内的属性。

问题原因 #

1. 结构不匹配：JSON的顶层是包含requesters数组的对象，但你的类定义了requester（单数）字符串字段，名称和类型都不兼容，导致序列化器将整个JSON内容作为字符串赋值给requester。
2. 字段类型错误：department_names和secondary_emails在JSON中是数组，你定义为string，即使结构匹配也无法正确映射。

解决方案 #

1. 修正类结构 #

需要定义两个类：一个对应JSON的顶层结构，一个对应requesters数组中的单个对象（按需保留字段即可）：

// 顶层根类，匹配JSON整体结构
public class RequestersRoot
{
    public List<PersonInfo> requesters { get; set; }
}

// 匹配requesters数组中的单个对象
public class PersonInfo
{
    public int id { get; set; }
    public string first_name { get; set; }
    public string last_name { get; set; }
    public string primary_email { get; set; }
    public List<string> department_names { get; set; }
    public List<string> secondary_emails { get; set; }
    public string mobile_phone_number { get; set; }
    public string work_phone_number { get; set; }
    public DateTime updated_at { get; set; }
    // 如需其他字段，直接从JSON中复制字段名并定义对应类型即可
}

注意：字段名必须和JSON完全一致（大小写敏感，可通过序列化选项忽略大小写）；数组类型字段需定义为List<T>；可空值类型（如int?）用于处理JSON中可能为null的数字字段。

2. 修改反序列化代码 #

将反序列化目标改为RequestersRoot，再从数组中提取目标对象：

using (HttpResponseMessage response = client.GetAsync(postMethod.ToString()).Result)
{
    if (response.IsSuccessStatusCode)
    {
        var json = response.Content.ReadAsStringAsync().Result;
        Console.WriteLine(json);

        // 反序列化为根类
        var root = JsonSerializer.Deserialize<RequestersRoot>(json);
        if (root?.requesters != null && root.requesters.Any())
        {
            // 取数组第一个对象（如需遍历所有对象，改用foreach循环）
            var person = root.requesters.First();
            Console.Write("id= " + person.id);
            Console.Write("first_name= " + person.first_name);
            Console.Write("department_names= " + string.Join(", ", person.department_names));
            // 其他字段按需输出
        }
    }
}

可选：忽略大小写配置 #

如果JSON字段名和类属性名大小写不一致，可添加序列化选项：

var options = new JsonSerializerOptions
{
    PropertyNameCaseInsensitive = true
};
var root = JsonSerializer.Deserialize<RequestersRoot>(json, options);

内容的提问来源于stack exchange，提问作者ghostfly