LINQ：加入5或6个表并逐个分组，然后对groupby数据进行计数

Question

表格是：从子级别到父级别：

  

TRAINING_TEACHER＆gt; TEACHER＆gt; INSTITUTE＆gt; SUBDISTRICT＆gt; DISTRICT   ZONE（DIVISION）

我需要显示学院名称，并且由SUBDISTRICT参加培训组的男女老师。我的视图模型是：

 public class TRAINING_STATUS_VIEW_MODEL
  {
    public int countMale { get; set; }
    public int countFemale { get; set; }
    public ZONE ZONE_VIEW_MODEL { get; set; }
    public DISTRICT DISTRICT_VIEW_MODEL { get; set; }
    public SUBDISTRICTUPAZILA_VIEW_MODEL { get; set; }
    public INSTITUTE INSTITUTE_VIEW_MODEL { get; set; }
  }

其中countMale，countFemale是TRAINING_TEACHER表中每个学院的教师数量。 TEACHER表中有一个性别列。 现在这里是我无法按学院和计数进行分组的查询。

var trainingStatusReport = 
from trainingTeacher in db.TRAINING_TEACHER 
join teacher in db.TEACHERs on trainingTeacher.TEACHER_NO equals teacher.TABLE_ID 
join institute in db.INSTITUTEs on teacher.INS_ID equals institute.INS_ID
join subDistrict in db.subDistricts on institute.LOC_ID equals (decimal)subDistrict.LOC_ID
join district in db.DISTRICTs on (decimal)subDistrict.DCODE equals (decimal)district.DCODE
join zone  in db.ZONEs on  district.ZC equals  zone.ZC   
select new TRAINING_STATUS_VIEW_MODEL { 
..........
.......... I can't go here
} ;

我已经通过institute.ins_id尝试了group institute，但无法在select部分编写代码。

Answer 1

使用进一步加入的分组是可能的，但可能效率低下。

是一个更好的联接替代方案

1. 使用导航属性
2. 使用let语句来简化任何其他复杂逻辑。

以下是如何将两者结合起来的示例。这会解决问题吗？

var trainingStatusReport =
    from trainingTeacher in db.TRAINING_TEACHER
    group trainingTeacher by trainingTeacher.Teacher.Institute into instituteGroup
    let institute = instituteGroup.Select(t => t.Teacher.Institute).FirstOrDefault()
    select new TRAINING_STATUS_VIEW_MODEL
    {
        countMale = instituteGroup.Count(t => t.Teacher.Gender == Male),
        countFemail = instituteGroup.Count(t => t.Teacher.Gender == Femail),
        ZONE = institute.SubDistrict.District.Zone,
        DISTRICT = institute.SubDistrict.District,
        SUBDISTRICT = institute.SubDistrict,
        INSTITUTE = institute
    };