LINQ獲得來自多個記錄的最新記錄列出

Question

我作爲

StudentName /教室/ GradeA/GradeB /格拉代茨/ GradeDate

學生教室是固定的，這樣列永遠不會改變的表。

每個學生都有不同的GradeDate的多個GradeA，GradeB和GradeC值。

public virtual IList<ClassroomDetail> GetLatestClassroomDetail(string classroom) 
    { 

     var query = from pc in _classroomDetailRepository.Table 
        where pc.Classroom == classroom 
        select pc; 

     var result = new List<ClassroomDetail>(query); 

     return result; 
    } 

上面的查詢返回一切，列表中有多個同樣的學生。

我怎樣才能得到最新的價值？

表：

ClassroomMaster

• 編號
• UpdateDate
• 課堂

---

ClassroomDetail

• 編號
• CM_ID（與ClassroomMaster標識外鍵）
• StudentName
• GradeA
• GradeB
• 格拉代茨
• GradeDate

在控制器

var bdetail = _classroomService.GetLatestClassroomDetail(classroom).OrderBy(d => d.StudentName); 

      var model = new List<ClassroomDetail>(); 
      foreach (var pr in bdetail) 
      { 

       model.Add(new ClassroomDetail 
       { 
        Id = pr.Id, 
        Classroom = pr.Classroom, 
        StudentName = pr.StudentName, 
        GradeA = pr.GradeA, 
        GradeB = pr.GradeB, 
        GradeC = pr.GradeC, 
        GradeDate = pr.GradeDate, 
       }); 
      } 


      return PartialView(model); 

Answer 1

這將解決你的問題由學生

 var query = _classroomDetailRepository.Table 
     .Where(a => a.Classroom == classroom)    
     .Select(b => b.OrderByDescending(y => y.GradeDate).Take(1).FirstOrDefault()); 

Answer 2

我終於找到了解決辦法：d

public virtual IList<ClassroomDetail> GetLatestClassroomDetail(string classroom) 
    { 
     var query = _classroomDetailRepository.Table 
      .Where(z => z.Classroom == classroom) 
      .GroupBy(x => x.StudentName)     
      .Select(x => x.OrderByDescending(y => y.GradeDate).Take(1).FirstOrDefault()); 

     var result = new List<BunkerPriceDetail>(query); 

     return result; 
    }