如何根据每个组中的基最大值选择list类属性？
如何根据每个组中的基最大值选择list类属性？
提问于 2015-12-29 11:45:25
如何根据每个组中的基最大值选择list类属性？我试过了，但没有成功。
public class STUDENT_DETAIL
{
public long? Registration_Id { get; set; }
public string Admission_No { get; set; }
public long? Class_Id { get; set; }
public long? Section_Id { get; set; }
public long? Academic_Year_Id { get; set; }
public string Student_First_Name { get; set; }
public string Student_Last_Name { get; set; }
public DateTime? Date_Of_Birth { get; set; }
public string Gender { get; set; }
public string Blood_Group { get; set; }
}
List<CUSTOM_STU_DETAIL> academicYr = new List<CUSTOM_STU_DETAIL>();
public PartialViewResult ReAdmission_of_Student(long? CompanyId, long? CompanyLocationId, long AcademicId, long? ClassID, long? SectionID)
{
if (CompanyId != null && CompanyId != 0 && CompanyLocationId != null && CompanyLocationId != 0 && ClassID != null && ClassID != 0 && SectionID != null && SectionID != 0)
{
academicYr = (from s in db.Student_Re_Admission
order by s.Re_Admission_Id descending
group s by s.Registration_Id into stugrp
//let topp = stugrp.Max(x => x.Re_Admission_Id)
select new CUSTOM_STU_DETAIL
{
}).ToList();
}
ViewBag.Student_List = StuList.ToList();
return PartialView();
}实际上，我想在linq中类似于下面的sql查询概念。
select * from [Student_Re_Admission] where [Re_Admission_Id] in( SELECT max(Re_Admission_Id) FROM [Student_Re_Admission] group by Registration_Id )回答 1
Stack Overflow用户
回答已采纳
发布于 2015-12-29 12:33:06
在Re_Admission_Id中没有STUDENT_DETAIL，所以使用Admission_No代替。
var maxReAdmissionIds =
(from s in db.Student_Re_Admission
group s by s.Registration_Id
into grp
select (grp.Max(p => Convert.ToInt32(p.Admission_No))).ToString())
.ToList();按Registration_Id分组，而不是首先选择列表中的Admission_No。
var result = from s in db.Student_Re_Admission
where maxReAdmissionIds.Contains(s.Admission_No)
select s;然后，使用列表来获得结果。
但另一个问题是，如果maxReAdmissionIds超过2100元素将导致"sql中太多的元素“异常。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/34510341
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