Question

我的数据库中有两个表picture和pictureratings。

public partial class picture
{
    public int idpicture { get; set; }
    public int iduser { get; set; }
    public string picTitle { get; set; }
    public string picFilename { get; set; }
    public System.DateTime pictime { get; set; }
    public int nuditylevel { get; set; }
    public int fakeslevel { get; set; }

    // This property will hold the total accumulated/summed 
    // up rating of a picture
    public int totalrating { get; set; }    
}

public partial class pictureratings 
{
    public int idrating { get; set; }
    public int idpictures { get; set; }
    public int iduser { get; set; }
    public System.DateTime iddatetime { get; set; }
    public int iduserrateddby { get; set; }
    public int rating { get; set; } 
}

对于每个评级，都会创建一个新的pictureratings行。我想按照图片ID对pictureratings表进行分组，然后对喜欢的内容进行计数。我想在picture属性的totalrating表中显示那些喜欢的内容。

根据我的研究到现在为止，我能够编写这段代码

var total = from p in db.picturedetails
            join l in db.picturelikes on p.idpictures equals l.idpictures 
            group l by l.idpictures into g
            select new 
            {
                IdUserPic = g.First().iduser,
                IdPictures = g.First().idpictures,
                totalrating = g.Count()    
            }

我使用web api返回查询总数。我的问题就出现了：如何显示picture属性，例如iduser，picTitle，picFilename，pictime，nuditylevel和{{1 }}？我做得对吗？我该怎么办？

Answer 1

我认为你正在寻找group join：

var total = from p in db.picturedetails
            join l in db.picturelikes on p.idpicture equals l.idpictures into pl
            select new
            {
                Picture = p,
                AverageRating = pl.Any()
                                    ? pl.Average(l => l.rating)
                                    : (double?)null,
                RatingsCount = pl.Count(),
                TotalRating = pl.Sum(l => (float?)l.likenumber) ?? 0
            };

如果图片没有偏好，则该图片的平均值为0和null。

Answer 2

您可以对匿名类进行分组。这样你就可以访问p＆amp; l属性。
看起来像这样：

var total = from p in db.picturedetails
            join l in db.picturelikes on p.idpictures equals l.idpictures 
            group new {p,l} by l.idpictures into g
            select new 
            {
                IdUserPic = g.First().p.iduser,
                IdPictures = g.First().p.nuditylevel,
                totalrating = g.Count()    
            }

使用Linq加入，分组和计数....面临麻烦

2 个答案: