Linq Query Return zero rows how to make left join with linq

Question

Hi i am facing a problem with my Linq query i have the following table

 

 

the issue is i am getting zero rows and when i inspect and bebug the query it says "Enumeration yielded no results"

 

below is my index method

public ActionResult Index()
{
ViewBag.PopulateGrades = _IEducation.PopulateGrade();
ViewBag.PopulatePrograms = _IEducation.PopulatePrograms();
ViewBag.PopulateStudents = _IEducation.PopulateStudents();
ViewBag.PopulateCourses = _IEducation.PopulateCourses();
ViewBag.PopulateModules = _IEducation.PopulateModules();
ViewBag.PopulateYear = _IYear.PopulateYears();
var StudentVSCourses = db.StudentCoursesAssigned.ToList();
ViewBag.Block_Id = new SelectList(db.Blocks, "Id", "Name");
ViewBag.Semester_Id = _ITeacherCoruses.PopulateSemsters();
using (DatabaseContext db = new DatabaseContext())
{
List<Student_Assigned_courses> Student_Assigned_courses = db.StudentCoursesAssigned.ToList();
List<Courses> courses = db.Courses.ToList();
List<Moduel> Module = db.Moduels.ToList();
List<Years> year = db.Years.ToList();
List<Semesters> semesters = db.Semesters.ToList();
List<Programs> Programs = db.Programs.ToList();
List<Student> students = db.Students.ToList();
List<Courses> curr = db.Courses.ToList();
List<Grade> grade = db.grades.ToList();
IEnumerable<Courses> h = db.Courses.ToList();
var employeeRecord = from e in Student_Assigned_courses
join d in students on e.Student_id equals d.Student_Id into table1
from d in table1.ToList()
join i in courses on e.Course_Id equals i.Course_Id into table2
from i in table2.ToList()
join m in Module on e.Module_Id equals m.Id into table3
from m in table3.ToList()
join y in year on e.Year_Id equals y.Id into table4
from y in table4.ToList()
join p in Programs on e.Program_Id equals p.Id into table5
from p in table5.ToList()
join g in grade on e.Grade equals g.Id into table6
from g in table6.ToList()
join s in semesters on e.Semster_Id equals s.Semester_Id into table7
from s in table7.ToList()
select new StudentCoursesViewModel
{
studentAssignedCourses = e,
courses = i,
programs = p,
//curses=curr,
curses = h,
semester = s,
studnets = d,
Year = y,
Modules = m,
grade = g,
};
return View(employeeRecord.ToList());
}

if i comment the yellow highlighted section than it returns the rows , can someone tell me how to adjust the linq query so that it should return the rows no matter even if the semester is null.