跳过实体框架核心 [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; }
}

我有一个查询，它返回已经包含书籍的图书馆：

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

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

我正尝试跳过5个库，然后再使用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，当我尝试执行 Skip 和 Take 方法，它将返回不包含书本的图书馆。

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.

如何可以使用跳过和接受并保存以前包含的实体吗？

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

推荐答案

通常，在使用 Skip 和 Take 方法。尝试按这种方式按名称排序：

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();

据我记得，您的查询应使用 OFFSET-FETCH 过滤器，该过滤器要求存在 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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