c# - 延迟加载 EF Core 2.1 不适用于身份？

Question

我按照这里的例子

https://learn.microsoft.com/en-us/ef/core/querying/related-data#lazy-loading

我的两个类看起来像这样

  public class RefMedSchool
{
    public int Id { get; set; }
    public string Code { get; set; }
    public string Name { get; set; }


    public virtual ICollection<ApplicationUser> ApplicationUser { get; set; }
}


 public class ApplicationUser : IdentityUser
{
    public string UserFirstName { get; set; }
    public string UserLastName { get; set; }
    public bool MustChangePassword { get; set; }


    public int? MedicalSpecialtyId { get; set; }
    [ForeignKey("RefMedicalSpecialtyForeignKey")]
    public RefMedicalSpecialty RefMedicalSpecialty { get; set; }


    public int RefMedSchoolId { get; set; }
    public virtual RefMedSchool RefMedSchool { get; set; }


    public UserProfileData UserProfileData { get; set; }


    public ICollection<UserFeedback> UserFeedbacks { get; set; }


    public ICollection<UserAction> UserActions { get; set; }


    public ICollection<UserProgram> UserPrograms { get; set; }
}

但是当尝试创建数据库时，出现以下错误。怎么了 ？这些属性根据需要是虚拟的。

System.InvalidOperationException: 'Navigation property 'RefMedicalSpecialty' on entity type 'ApplicationUser' is not virtual. UseLazyLoadingProxies requires all entity types to be public, unsealed, have virtual navigation properties, and have a public or protected constructor.'

Answer 1

Entity Framework Core 2.1 引入了延迟加载。如问题 Lazy-loading proxies: allow entity types/navigations to be specified 中所述，它要求所有 导航属性都是虚拟的:

Currently when lazy-loading proxies are used every entity type in the model must be suitable to proxy and all navigations must be virtual. This issue is about allowing some entity types/navigations to be lazy-loaded while others are not.

问题仍未解决且未解决，因此仍不支持您想要的方案。

正如异常告诉您的那样:

UseLazyLoadingProxies requires all entity types to be public, unsealed, have virtual navigation properties, and have a public or protected constructor.

因此，将所有导航属性(即引用其他实体的属性)更改为虚拟。

或使用 ILazyLoader，如 Lazy-loading without proxies 中所述:

public class Blog
{
    private ICollection<Post> _posts;

    public Blog()
    {
    }

    private Blog(ILazyLoader lazyLoader)
    {
        LazyLoader = lazyLoader;
    }

    private ILazyLoader LazyLoader { get; set; }

    public int Id { get; set; }
    public string Name { get; set; }

    public ICollection<Post> Posts
    {
        get => LazyLoader?.Load(this, ref _posts);
        set => _posts = value;
    }
}