JSON转C#对象时出现Object null的问题求助

接口返回的JSON示例 #

[
    {
        "id": 1,
        "firstName": "John",
        "lastName": "Smith",
        "company": {
            "id": 19297,
            "identifier": "XYZTestCompany",
            "name": "XYZ Test Company",
            "_info": {
                "company_href": "zzzzzzzzzzzz",
                "mobileGuid": "2685633f-6375-43"
            }
        },
        "site": {
            "id": 1502,
            "name": "Main",
            "_info": {
                "site_href": "zzzzzzzzz"
            }
        },
        "inactiveFlag": false,
        "title": "President",
        "marriedFlag": false,
        "childrenFlag": false,
        "unsubscribeFlag": false,
        "gender": "Male",
        "mobileGuid": "afghgfdfgh",
        "defaultPhoneType": "Direct",
        "defaultPhoneNbr": "00000000",
        "defaultBillingFlag": false,
        "defaultFlag": false,
        "companyLocation": {
            "id": 1,
            "name": "Company",
            "_info": {
                "location_href": "zzzzzzzz"
            }
        },
        "communicationItems": [
            {
                "id": 10,
                "type": {
                    "id": 2,
                    "name": "Name",
                    "_info": {
                        "type_href": "zzzzzzz"
                    }
                },
                "value": "8",
                "defaultFlag": true,
                "communicationType": "Phone"
            }
        ],
        "types": [
            {
                "id": 2,
                "name": "Name",
                "_info": {
                    "type_href": "zzzzzzzz"
                }
            }
        ],
        "customFields": [
            {
                "id": 41,
                "caption": "Type",
                "type": "Text",
                "entryMethod": "List",
                "numberOfDecimals": 0
            },
            {
                "id": 42,
                "caption": "Synce",
                "type": "Checkbox",
                "entryMethod": "EntryField",
                "numberOfDecimals": 0
            }
        ],
        "ignoreDuplicates": false,
        "_info": {
            "lastUpdated": "2015-10-03T05:59:47Z",
            "updatedBy": "Portal",
            "communications_href": "z",
            "notes_href": "z",
            "tracks_href": "z",
            "portalSecurity_href": "z",
            "activities_href": "z",
            "documents_href": "z",
            "configurations_href": "z",
            "tickets_href": "z",
            "opportunities_href": "z",
            "projects_href": "z",
            "image_href": "z"
        }
    }
]

自定义C#实体类 #

public class ContactJson
{
    public List<Contact> Contact { get; set; }
}
public class Contact
{
    public int id { get; set; }
    public string firstName { get; set; }
    public string lastName { get; set; }
    public Company company { get; set; }
    public string site { get; set; }
    public bool inactiveFlag { get; set; }
    public string title { get; set; }
    public bool marriedFlag { get; set; }
    public bool childrenFlag { get; set; }
    public bool unsubscrubeFlag { get; set; }
    public string gender { get; set; }
    public string mobileGuid { get; set; }
    public string defaultPhoneType { get; set; }
    public string defaultPhoneNbr { get; set; }
    public bool defaultbillingflag { get; set; }
    public bool defaultFlag { get; set; }
    public string companyLocation { get; set; }
    public string communicationItems { get; set; }
    public string types { get; set; }
    public string customFields { get; set; }
    public bool ignoreDuplicates { get; set; }
    public string info { get; set; }
}
public class Company
{
    public int id { get; set; }
    public string name { get; set; }
    public string info { get; set; }
}

反序列化代码 #

var ConnectwiseClient = new RestClient("https://api-aus.myconnectwise.net/v4_6_release/apis/3.0//company/contacts/");
var request = new RestRequest()
{
    Method = Method.Get,
    Timeout = 300000
};
request.AddHeader("clientID", "");
ConnectwiseClient.Authenticator = new HttpBasicAuthenticator("");

var response = ConnectwiseClient.Execute(request);

var result = JsonConvert.DeserializeObject<List<ContactJson>>(response.Content);

问题现象 #

接口返回25条数据，反序列化后result包含25个元素，但所有元素均为null，而response.Content存在有效JSON内容。

排查与修复方案 #

• 根类型不匹配：接口返回的是Contact对象的数组（[]包裹），但反序列化时用了List<ContactJson>，而ContactJson内部包含List<Contact>，结构完全不匹配。应直接反序列化为List<Contact>：

  var result = JsonConvert.DeserializeObject<List<Contact>>(response.Content);
  

• 属性名称/拼写错误：
  • JSON中的unsubscribeFlag在实体类中写成unsubscrubeFlag（拼写错误），导致无法映射
  • JSON中的defaultBillingFlag在实体类中写成defaultbillingflag（大小写不匹配，默认序列化规则区分大小写）
  • JSON中的_info在实体类中写成info，名称不一致，需添加JsonProperty特性修正：

    [JsonProperty("_info")]
    public string info { get; set; }
    

• 复杂类型错误声明为字符串：JSON中的site、companyLocation、communicationItems、types、customFields都是对象/数组类型，但实体类中声明为string，无法完成映射。需为这些类型定义对应实体类，例如：

  public class Site
  {
      public int id { get; set; }
      public string name { get; set; }
      [JsonProperty("_info")]
      public SiteInfo Info { get; set; }
  }
  public class SiteInfo
  {
      public string site_href { get; set; }
  }
  

  然后将Contact类中的site属性改为public Site site { get; set; }，同理处理其他复杂类型。
• Company类缺失属性：JSON中的company包含identifier字段，实体类中未定义，若需要该字段需补充；同时_info字段也需要添加对应实体类和JsonProperty特性。

内容的提问来源于stack exchange，提问作者ethan