Update data in multiple table relation(employee and employeecourse tables) - asp.net-mvc-4

Question

I have two tables employee and employee course in a one-to-many relation.
Needs: update name in table employee and courseid in employeecourse table in edit view
Problem: when click submit button in edit view it delete all data and save only selected
Courses from drop down courses just now
If no changes happen to courses by(add or remove courses) when click submit
Button it delete all
code logic
I try to using logic to delete all data when click submit then save all data
after changes
meaning submit button do two task
delete courses exist before for the employee i edit view
add the courses after all changes done in edit view for this employee
see image below
code
model class EditEmployeeVm
public class EditEmployeeVm
{
public int Id { set; get; }
public string Name { get; set; }
public List<SelectListItem> Courses { get; set; }
public int[] CourseIds { set; get; }
public List<CourseVm> ExistingCourses { set; get; }
}
public class CourseVm
{
public int Id { set; get; }
public string Name { set; get; }
}
in edit function get i pass data to edit view
public ActionResult Edit(int id)
{
var vm = new EditEmployeeVm { Id = id };
var emp = db.Employees.FirstOrDefault(f => f.Id == id);
vm.Name = emp.Name;
vm.ExistingCourses = db.EmployeeCourses
.Where(g => g.EmployeeId == id)
.Select(f => new CourseVm
{
Id = f.Id,
Name = f.Course.CourseName
}).ToList();
vm.CourseIds = vm.ExistingCourses.Select(g => g.Id).ToArray();
vm.Courses = db.Courses.Select(f => new SelectListItem
{
Value = f.Id.ToString(),
Text = f.CourseName
}).ToList();
return View(vm);
}
[HttpPost]
public ActionResult Edit(EditEmployeeVm model)
{
**//i need to save name employee changes in employee table and all courses changes in emloyeecourse table
//what is wrong here**
var emp = db.Employees
.Include(e => e.EmployeeCourses)
.FirstOrDefault(f => f.Id == model.Id);
foreach (var eec in emp.EmployeeCourses.ToList())
{
db.EmployeeCourses.Remove(eec);
}
foreach (var couseid in model.CourseIds)
{
db.EmployeeCourses.Add(new EmployeeCourse { CourseId = couseid, EmployeeId = emp.Id });
}
db.SaveChanges();
return View();
}
update
public ActionResult Edit(EditEmployeeVm model)
{
var emp = db.Employees.FirstOrDefault(f => f.Id == model.Id);
foreach (var couseid in model.CourseIds)
{
db.EmployeeCourses.Add(new EmployeeCourse { CourseId = couseid, EmployeeId = emp.Id });
db.SaveChanges();
}
return View();
}
I Try in code above under update section
i can add data and save when click submit button
but problem when click remove button to course by jquery
it remove it but it not save changes of remove in database
so that when open edit view again i see item i removed before
how to solve that when click submit button to save item removed in database