在这里我们有一个图书与其章节的一对多关系。我们需要知道如何更新这个关系中的嵌套项。假设我们要更新某本书的某个章节的内容。

模型：

public class Book
{
    public int BookId { get; set; }
    public string BookTitle { get; set; }
    public ICollection Chapters { get; set; }
}

public class Chapter
{
    public int ChapterId { get; set; }
    public string ChapterTitle { get; set; }
    public string ChapterContent { get; set; }
    public int BookId { get; set; }
    public Book Book { get; set; }
}

控制器方法：

[HttpPut("{bookId}/chapters/{chapterId}")]
public async Task UpdateChapter(int bookId, int chapterId, [FromBody] Chapter chapter)
{
    if (bookId != chapter.BookId || chapterId != chapter.ChapterId)
    {
        return BadRequest("Request Ids does not match with the body.");
    }

    var existingChapter = await _context.Chapters
        .Include(b => b.Book)
        .SingleOrDefaultAsync(c => c.BookId == bookId && c.ChapterId == chapterId);

    if (existingChapter == null)
    {
        return NotFound();
    }

    existingChapter.ChapterTitle = chapter.ChapterTitle;
    existingChapter.ChapterContent = chapter.ChapterContent;

    try
    {
        await _context.SaveChangesAsync();
    }
    catch (DbUpdateConcurrencyException)
    {
        if (!ChapterExists(bookId, chapterId))
        {
            return NotFound();
        }
        else
        {
            throw;
        }
    }
    return NoContent();
}

在这个方法中，我们首先检查提交的章节的ID是否与请求的ID匹配。然后，我们在数据库中查找现有章节，更新了章节内容后存储更改。如果出现并发异常，则检查章节是否存在。如果章节不存在