如何在使用groupby時加入

Question

我在mydatabase中有兩張圖片和圖片喜歡的表。

public partial class picturedetail 
{ 
    public int idpictures { 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 likes { get; set; } 
    public int nuditylevel { get; set; } 
    public int fakeslevel { get; set; } 
} 

    public partial class picturelike 
{ 
    public int idpicturelike { get; set; } 
    public int idpictures { get; set; } 
    public int iduser { get; set; } 
    public System.DateTime iddatetime { get; set; } 
    public int iduserlikedby { get; set; } 
    public int likenumber { get; set; } 
} 

它我的數據傳輸對象（DTO），以避免匿名類型錯誤

public class LikesandPictureDetails 
{ 
    public int IdPicturess { get; set; } 
    public int IdUserPic { get; set; } 
    public string PicTitle { get; set; } 
    public string picFilename { get; set; } 
    public System.DateTime? PicTime { get; set; } 
    public int Likes { get; set; } 
    public int NudityLevel { get; set; } 
    public int FakesLevel { get; set; } 
    public int IdPicturelike { get; set; } 
    public int IdUser { get; set; } 
    public System.DateTime? IdDatetime { get; set; } 
    public int IduserLikedby { get; set; } 
    public int LikeNumber { get; set; } 
    public int IdPictures { get; set; } 
    public float totalrating { get; set; } 
    public int Count { get; set; } 
} 

我能夠成功地算圖片的個體評級，然後通過他們的計數分。現在我想在我的照片細節表中顯示總計。如何實現這件事？這是我的代碼：

var query = 
      db.picturelikes.GroupBy(n => n.idpictures).Select(group => 
        new LikesandPictureDetails 
        { 
         IdPictures = group.Key, 
         totalrating = (group.AsEnumerable().Sum(o => o.individualrating))/group.Count(), 

        }); 

這裏likesandpicturedetails是充當dto。

Answer 1

那麼，首先你應該使用方法Average來計算平均值。但是，在你的情況 但是，你需要計算整體評價，你爲什麼不計算總和與平均值在相同的步驟：

db.picturelikes.GroupBy(n => n.idpictures).Select(group => 
new LikesandPictureDetails 
{ 
    IdPictures = group.Key, 
    averageRating = (group.AsEnumerable().Average(o => o.individualrating)), 
    totalRating = (group.AsEnumerable().Sum(o => o.individualrating)),  
});