实体框架核心v6.0.5外国密钥属性返回意外的null

Question

我从aspnetusers sidentityuser 的扩展名读取loginuser aspnetusers 带有实体框架核心core v6.0.5的表。

当我尝试阅读其外国密钥属性公司时，该属性始终为空 - 为什么？

IE

var user = dbContext.Users
                    .FirstOrDefault(...);// A non-null LoginUser is returned

var companyId = user.CompanyId; // results in Integer 1 - as expected

var company = user.Company; // company is always null

表定义：

public class LoginUser : IdentityUser
{
    public int CompanyId { get; set; } = -1;
    public virtual Company Company { get; set; }
}

public class Company
{
    public int Id { get; set; } = 0;
    public virtual ICollection<LoginUser> LoginUsers { get; set; }
    [Required]
    [MaxLength(128)]
    public string TradingName { get; set; } = string.Empty;
}

loginuser为列生成的company> companyId生成的外键索引。

有什么想法我要做什么？

aspnetusers表数据：

Id                                      CompanyId   Other User fields not shown...
8c568150-ecf8-46f4-8ec1-db9a7a66daaa    1   

公司表数据：

Id  TradingName 
-----------------------
-1  Unassigned Company
1   Discovery