Question

我想使用LINQ执行以下查询：

所有单位数
所有单位的总得分和总得分
平均值：得分分数％总分* 100 4）排名
基于得分的排名（如果user1完成2个单元ID为100和101的单元，则应与其他用户进行比较）

数据库：

PRODUCTS

代码：

SELECT U.USER_NAME, U.USER_EMAIL, U.USER_PHONE, U.USER_AVATAR, U.ABOUT
FROM USERS AS U
WHERE U.USER_ID = '${user_id}'
SELECT B.PRODUCT_ID
FROM BOOKMARKS_PRODUCTS AS B
WHERE B.USER_ID = '${user_id}'
SELECT P.*
FROM PRODUCTS AS P
WHERE P.PRODUCT_ID = '${product_id}'

Answer 1

您改编的函数以及我介绍的用于存储结果的额外类：

public class UserRankObject
{
    public int Rank { get; set; }
    public int UserId { get; set; }
    public float AverageScore { get; set; }
}
public UserRankObject GetUserRankObject(int? Student_ID, int? CourseID, int? SemID, int? SubjectID)
{
    // TODO: add null checks for arguments, or make them non-nullable.
    var scoreCard =
        dbcontext.Stu_Result
            .Where(u => u.CourseID == CourseID
                     && u.SemID == SemID
                     && u.SubjectID == SubjectID);

    return scoreCard.GroupBy(u => u.UserID)
       .OrderByDescending(g => g.Average(u => u.ScoredMarks / u.TotalMarks * 100))
       .Select((g, i) => new UserRankObject
       {
           UserId = g.Key,
           Rank = i + 1,
           AverageScore = g.Average(u => u.ScoredMarks / u.TotalMarks * 100)
       })
       .Single(u => u.UserId == Student_ID);
}

用法：

var ranked = new List<UserRankObject>()
{
    GetUserRankObject(1022, 109, 3000, 2006),
    GetUserRankObject(1021, 109, 3000, 2006)
};
Console.WriteLine("Ranked: \n" + string.Join("\n", ranked.Select(r => $"{r.Rank}. {r.UserId} ({r.AverageScore})")));
/*
Ranked:
1. 1022 (77.5)
2. 1021 (51.66667)
*/

Answer 2

public GetCalculatePerform(int? Student_ID, int? CourseID, int? SemID, int? SubjectID)
{           
    var scoreCard = dbcontext.Stu_Result
    .Where(u => u.CourseID == CourseID && u.SemID == SemID && u.SubjectID == SubjectID )
    .ToList()
    .GroupBy(u => u.UserID)
    .OrderByDescending(grp => grp.Average(u => u.ScoredMarks))
    .Select((grp, i) => new
    {
        UserId = grp.Key,
        Rank = i + 1,
        AverageScore = grp.Average(u => u.ScoredMarks)
    }).ToList().Single(u => u.UserId == Student_ID);
}

Answer 3

 public class GetCalculatePerform
    {

 abcEntities dbcontext = new abcEntities();

        public UserRankObject tempobj { get; set; }


        //********************************************************Performance & Rank Calculation********************************************


      public  GetCalculatePerform(int? Student_ID, int? CourseID, int? SemID, int? SubjectID)
        {


                var scoreCard = dbcontext.Stu_Result
                .Where(u => u.CourseID == CourseID && u.SemID == SemID && u.SubjectID == SubjectID)
                .ToList()
                .GroupBy(u => u.UserID)
                .OrderByDescending(grp => grp.Average(u => u.ScoredMarks))
                .Select((grp, i) => new UserRankObject
                {
                    UserId = grp.Key,
                    Rank = i + 1,
                    AverageScore = grp.Average(u => u.ScoredMarks)
                }).ToList().Single(u => u.UserId == Student_ID);
                // .FirstOrDefault(u=>u.UserId == Student_ID);


                this.tempobj = scoreCard;


      }

    }

如何在LINQ中执行以下查询？

3 个答案: