.NET Core 6中为IdentityUser关联更多表的问题排查

现有基础实现 #

我已基于IdentityUser实现登录功能，自定义了关联AspNetUsers表的CoreUser类：

public class CoreUser: IdentityUser<string>
{
    public User User { get; set; }
}

关联需求与POCO类配置 #

我希望通过UserManager调用用户关联的更多数据表，目前尝试关联Registrations表与User表：

• User表包含指向Registration表的外键RegistrationId，关联Registration表
• Registration表还需关联VerificationAgency表

已在POCO类中定义关联：

User类代码 #

[Required]
[Display(Name = "Registration ID")]
[ForeignKey("RegistrationId")]
public System.Guid RegistrationId { get; set; }
public virtual Registration Registration { get; set; }

Registration类代码 #

public ICollection<User> Users { get; set; }
public ICollection<VerificationAgency> Verifications { get; set; }

问题现象 #

Registration及其关联的Verifications属性始终返回null。

当前配置与查询代码 #

OnModelCreating配置 #

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    base.OnModelCreating(modelBuilder);

    modelBuilder.Entity<CoreUser>()
            .HasOne(a => a.User)
            .WithOne()
            .HasForeignKey<User>(a => a.AspNetUsersId)
            .OnDelete(DeleteBehavior.Cascade);

    modelBuilder.Entity<CoreRole>();

        //自动注册所有实现IEntityTypeConfiguration的配置类
    modelBuilder.ApplyConfigurationsFromAssembly(Assembly.GetExecutingAssembly());
}

登录用户查询代码 #

private User _loggedInUser;

protected User LoggedInUser
{
    get
    {
        if (_loggedInUser == null)
        {
            var userWhere = _userManager.Users
                                        .Where(x => x.UserName == User.Identity.Name);

            _loggedInUser = userWhere.Select(user => user.User)
                                     .Include(x => x.Registration)
                                     .Include(x => x.Registration.Verifications)
                                     .FirstOrDefault();
        }

        return _loggedInUser;
    }
}

已尝试的Registration映射配置 #

builder.HasMany(x => x.Users)
       .WithOne(x => x.Registration)
       .HasForeignKey(x => x.RegistrationId);

builder.HasMany(x => x.Verifications)
       .WithOne(x => x.Registration)
       .HasForeignKey(x => x.RegistrationId);

请问是否遗漏了映射配置，或者无法为用户表关联额外数据表？（附数据库结构截图：User表含RegistrationId外键，Registration表与VerificationAgency表存在关联）

内容的提问来源于stack exchange，提问作者Mohammed Ismail