跳过并接受 Entity Framework Core [英] Skip and Take in Entity Framework Core

问题描述

我有简单的 POCO 类:

I have simple POCO classes:

public class Library
{
    [Key]
    public string LibraryId { get; set; }

    public string Name { get; set; }

    public List<Book> Books { get; set; }
}

public class Book
{
    [Key]
    public string BookId { get; set; }

    public string Name { get; set; }

    public string Text { get; set; }
}

我有查询，返回包含已包含书籍的图书馆:

And I have query, that returns libraries with already included books:

dbContext.Set<Library>.Include(x => x.Books);

我试图跳过 5 个库，然后选择其中的 10 个:

I'm trying to skip 5 libraries and then take 10 of them:

await dbContext.Set<Library>.Include(x => x.Books).Skip(5).Take(10).ToListAsync();

问题是，当我尝试在此查询上执行 Skip 和 Take 方法时，它返回没有包含书籍列表的图书馆.

The problem is, that when I'm trying to perform Skip and Take methods on this query, it returns libraries without included list of books.

如何使用 Skip 和 Take 保存以前包含的实体?

How can I work with Skip and Take, with saving previously included entities?

推荐答案

通常你需要先Order By，然后才能使用Skip 和Take 方法.尝试按名称这样排序:

Usually you need to Order By first before use Skip and Take methods. Try ordering by name like this way:

await dbContext.Set<Library>().Include(x => x.Books)
                              .OrderBy(x=>x.Name)
                              .Skip(5)
                              .Take(10)
                              .ToListAsync();

据我所知，您的查询应该使用 OFFSET-FETCH 过滤器进行翻译，该过滤器需要存在 ORDER BY 子句.

As far as I remember your query should be translated using OFFSET-FETCH filter which requires an ORDER BY clause to exist.

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