无法弄清楚如何做到在LINQ多加入EF英孚

Question

TL;博士版本：我需要这个SQL语句使用LINQ合作，EF

这是在SQL查询：

select 
stu.SyStudentId, 
rtrim(stu.StuNum) as StudentNumber, 
stu.SSN, 
stu.FirstName, 
stu.LastName, 
Email, 
OtherEmail, 
stu.StartDate, 
case 
when (systa.category = 'E') then 'Enrolled' 
    when (systa.category = 'A') then 'Active' 
    else 'This should never happen' 
end as StatusCategory, 
rtrim(schsta.Code) as SchoolStatusCode, 
pic.StudentPicture, 
case when (stu.DateLstMod > isnull(pic.DateLstMod,'1900-1-1')) 
then stu.DateLstMod 
    else pic.DateLstMod 
end as DateLstMod 
from 
SyStudent stu 
inner join syschoolstatus schsta on schsta.syschoolstatusid = stu.syschoolstatusid 
inner join SyStatus systa on systa.SyStatusId = schsta.SyStatusId 
left outer join cmstudentpicture pic on pic.systudentid = stu.systudentid 
where stu.sycampusid = 6 
and systa.category in ('E','A') 

丑陋查询，从旧系统继承..

我试图得到一些我们必须利用实体框架的服务。我试图让这个查询使用该方法基于语法的工作。我第一次拿到我要加盟的所有对象的列表：

var students = ctx.syStudents.ToList(); //root 
var statusCode = ctx.SySchoolStatus.ToList(); //inner 
var status = ctx.syStatus.ToList(); //inner 
var picture = ctx.CmStudentPictures.ToList(); //left outer 

“CTX”是我的DbContext类。

查询我到目前为止是这样的：

var query = students 
    .GroupJoin(statusCode, 
    student => student.SySchoolStatusID, 
    statuscode => statuscode.SySchoolStatusID, 
    (student, studentStatusCode) => new 
    { 
     StudentName = student.FirstName 
    }); 

显然没有完全实现，但我试图得到一个想法，如果这是执行最好的办法，因为我有几个内部连接，然后左外连接为好，或者是有没有得到这个工作更好，更易读的方式？

Answer 1

我肯定会推荐查询语法在lambda语法进行连接。

试试沿着这些线路：

var result = 
from stu in SyStudent 
join schsta in syschoolstatus on stu.syschoolstatusid equals schsta.syschoolstatusid //inner 
join systa in SyStatus on schsta.SyStatusId equals systa.SyStatusId //innner 
from pic in cmstudentpicture.Where(x => x.systudentid = stu.systudentid).DefaultIfEmpty() //outer 
where stu.sycampusid = 6 
select new{ 
    stu, 
    schsta, 
    systa, 
    pic 
};