Question

自从我上次使用内连接以来，我已经好几年了，所以我有点生疏了。它有3个表

相册，相册图片和用户

现在我首先在我的存储库中内部加入相册和AlbumsImages，我只想要第一个来自albumsimages的第一个来自firs封面描述然后Id描述（AlbumImages中可以有0个图像！）。之后，我加入我的用户表，在用户ID中加载用户ID。我的问题是我不会只获得一张专辑，而是每张专辑中的每张图片的结果，我只想要1张。我在这做错了什么？

    public IQueryable<Album> Get()
    {
        return (from a in context.Albums
                join i in _imageRepository.Get() on a.Id equals i.AlbumId into albumImages
                from cover in albumImages.DefaultIfEmpty()
                orderby cover.Cover descending, cover.Id ascending 
                select new Album()
                    {
                        Id = a.Id,
                        UserId  = a.UserId,
                        Name  = a.Name,
                        Created  = a.Created,
                        LastEdit  = a.LastEdit,
                        Description  = a.Description,
                        Views  = a.Views,
                        Location  = a.Location,
                        Photoshoot  = a.Photoshoot,
                        Cover = cover,
                    });
    }

var albums = (from a in AlbumRepository.Get()
                            join u in UserRepository.Get() on a.UserId equals u.Id
                            orderby a.Id descending
                            select new AlbumDisplayModel()
                                {
                                    Album = a,
                                    User = u
                                }).ToList();

测试：

    return (from i in _imageRepository.Get()
            join album in context.Albums on i.AlbumId equals album.Id into albums
            from a in albums.DefaultIfEmpty()
            select new Album()
                {
                    Id = a.Id,
                    UserId  = a.UserId,
                    Name  = a.Name,
                    Created  = a.Created,
                    LastEdit  = a.LastEdit,
                    Description  = a.Description,
                    Views  = a.Views,
                    Location  = a.Location,
                    Photoshoot  = a.Photoshoot,
                    Cover = i,
                });

Answer 1

从DefaultIfEmpty取消albumImages。无论是否匹配（左连接），都会返回专辑图像。

内部左连接linq返回太多结果

1 个答案: