使用Linq加入，分組和計數....面臨麻煩

Question

我有兩個表，picture和pictureratings在我的分貝。

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; } 
} 

對於每個評級，將創建一個新的pictureratings行。我想通過圖片ID將pictureratings表分組，然後計算喜歡的。我想在picture表中顯示那些喜歡totalrating屬性的表。

所以按照我的研究到現在，我可以寫這樣的代碼

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()  
      } 

我使用的Web API返回的查詢總數。因此，我的問題來了：如何顯示picture屬性，如iduser,picTitle,picFilename,pictime,nuditylevel和fakeslevel？我做對了嗎？我應該怎麼做？

Answer 1

您可以對一個匿名類進行分組。這樣你就可以訪問兩個p屬性。
是這樣的：

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()  
      } 

Answer 2

我覺得group join是你在找什麼：

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 
      }; 

如果圖片有沒有喜歡的，這會給一個0總數和平均null該圖片。