在我的.NET 7 Web API中，尽管dependent（Researcher）正确地包含了parents id属性，但parent（User）上的navigation属性仍然为null。我试图在AuthService中同时创建User和Researcher。如果您能帮助我如何让User包含对Researcher的引用，我将不胜感激。

**编辑：**经过进一步测试，我发现User.Researcher和Researcher.User都是null，我唯一的参考是Researcher.UserId是正确的。

The API response:

[
  {
    "userId": "d8725e37-b3b2-4851-8ae7-07afadb92adc",
    "email": "a@email.com",
    "passwordHash": "$2a$11$hfvUxb44m.b0/RYWBwyQvuaxF0mcRhmiGmqjldvOlDiAmnOiHF92i",
    "researcher": null
  },
  {
    "userId": "3eb55b33-8c41-405e-a19c-5390c472302e",
    "email": "b@email.com",
    "passwordHash": "$2a$11$uwvZErMttnzYRpwUO2LfOOvvjURZrSs5V68lp2L8.MtC6gubs7bkO",
    "researcher": null
  },
  {
    "userId": "b2fc3e76-02c5-48a4-b865-b686870e429a",
    "email": "c@email.com",
    "passwordHash": "$2a$11$hKDeNsfK5qnPf5uFujKgu.LB5d/FSDVFnj.vN49vAmd.zZn/ogaLW",
    "researcher": null
  }
]

The api schema:

[
  {
    "userId": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
    "email": "string",
    "passwordHash": "string",
    "researcher": {
      "researcherId": 0,
      "firstName": "string",
      "lastName": "string",
      "field": "string",
      "areaOfFocus": "string",
      "biography": "string",
      "user": "string",
      "joinEntities": [
        {
          "researcherArticleId": 0,
          "researcherId": 0,
          "researcher": "string",
          "articleId": 0,
          "article": {
            "articleId": 0,
            "title": "string",
            "url": "string",
            "articleData": "string",
            "joinEntities": [
              "string"
            ]
          }
        }
      ]
    }
  }
]

User.cs父项：

public class User
    {
        public Guid UserId { get; set; } = Guid.NewGuid();
        public string Email { get; set; } = string.Empty;
        public string PasswordHash { get; set; } = string.Empty;
        public Researcher? Researcher { get; set; }
    }

Researcher.cs相关：

public class Researcher
    {
        [Key]
        public int ResearcherId { get; set; }
        public string FirstName { get; set; } = string.Empty;
        public string LastName { get; set; } = string.Empty;
        public string Field { get; set; } = string.Empty;
        public string AreaOfFocus { get; set; } = string.Empty;
        public string Biography { get; set; } = string.Empty;
        [ForeignKey("UserId")]
        public User? User { get; set; }
        public List<ResearcherArticle>? JoinEntities { get; set; }

    }

AuthService.cs方法，用于在同一个调用中创建User和Researcher：

public async Task<ServiceResponse<UserRegisterResponseDto>> RegisterUser(UserRegisterRequestDto request)
        {
            List<string> userValidationMessages = ValidateUser(request);

            var serviceResponse = new ServiceResponse<UserRegisterResponseDto>() { };

            if (userValidationMessages.Count > 0)
            {
                serviceResponse.Success = false;
                serviceResponse.Messages = userValidationMessages;
                return serviceResponse;
            }

            string passwordHash
                = BCrypt.Net.BCrypt.HashPassword(request.Password);
            User userToReturn = new()
            {
                Email = request.Email,
                PasswordHash = passwordHash
            };

            Researcher reasercherToAdd = new()
            {
                User = userToReturn,
            };

            _db.Researchers.Add(reasercherToAdd);

            userToReturn.Researcher = reasercherToAdd;
            _db.Users.Add(userToReturn);
            bool userAdded = await _db.SaveChangesAsync() > 0;

            if (!userAdded)
            {
                serviceResponse.Success = false;
                serviceResponse.Messages = new List<string>() { userAdded.ToString() };
                return serviceResponse;
            }

            serviceResponse.Success = true;
            serviceResponse.Messages = new List<string>() { "Registration successful" };
       
            return serviceResponse;
        }