C# 在实体框架核心中选择多个+选择后包括不工作

我使用EntityFrameworkCoreV2进行了这个查询，但是Include/thenclude没有像我预期的那样工作。以下是查询：

 var titlesOwnedByUser = context.Users
                   .Where(u => u.UserId == userId)
                   .SelectMany(u => u.OwnedBooks)
                   .Select(b => b.TitleInformation)
                   .Include(ti => ti.Title)
                   .ThenInclude(n => n.Translations);

查询可以工作，但是我得到的标题设置为null

为了澄清，这些课程是

class User 
{
     public int Id { get; set; }
     public List<BookUser> OwnedBooks { get; set; }
}

class Book 
{
    public int Id { get; set; }
    public TitleInformation TitleInformation { get; set; }
    public List<BookUser> Owners { get; set; }
}

class BookUser 
{
     public int BookId { get; set; }
     public int UserId { get; set; }
     public Book Book { get; set; }
     public User User { get; set; }
}

class MyContext
{
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
        modelBuilder.Entity<BookUser>()
            .HasOne(x => x.User)
            .WithMany(x => x.OwnedBooks)
            .HasForeignKey(x => x.UserId);

        modelBuilder.Entity<BookUser>()
            .HasOne(x => x.Book)
            .WithMany(x => x.Owners)
            .HasForeignKey(x => x.BookId);
     }
}

class TitleInformation
{
    public int Id { get; set; }
    public Title Title { get; set; }
    public Title Subtitle { get; set; }
}

class Title
{
     public int Id { get; set; }
     public string OriginalTitle { get; set; }
     public List<Translation> Translations { get; set; }
}

---

要在返回的查询中加载翻译，我必须做些什么？

这是当前的EF核心限制，如中所述：

如果更改查询，使其不再返回查询开始时的实体类型的实例，则会忽略include运算符

因此，您需要从context.Set启动查询。但为了生成所需的过滤，您需要从TitleInformation到Book的反向导航属性，该属性当前在您的模型中缺失：

class TitleInformation
{
    // ...
    public Book Book { get; set; } // add this and map it properly with fluent API
}

一旦你有了它，你可以用这样的东西：

var titlesOwnedByUser = context.Set<TitleInformation>()
    .Include(ti => ti.Title)
        .ThenInclude(n => n.Translations)
    .Where(ti => ti.Book.Owners.Any(bu => bu.UserId == userId));

分别为：

var titlesOwnedByUser = context.Set<TitleInformation>()
    .Include(ti => ti.Title)
        .ThenInclude(n => n.Translations)
    .Where(ti => ti.Books.SelectMany(b => b.Owners).Any(bu => bu.UserId == userId));

---

你能显示实体的配置吗？听起来像。您应该从context.TitleInformation开始以其他方式构建查询。@H.Herzl请检查更新操作。@IvanStoev我怎么知道如何开始？你能把代码写进去吗？我有点迷路了：可能是重复的

var titlesOwnedByUser = context.Set<TitleInformation>()
    .Include(ti => ti.Title)
        .ThenInclude(n => n.Translations)
    .Where(ti => ti.Books.SelectMany(b => b.Owners).Any(bu => bu.UserId == userId));