private void PopulateAssignedCourseData(Instructor instructor)
{
 var allCourses = db.Courses;
 var instructorCourses = new HashSet<int>(instructor.Courses.Select(c =>
c.CourseID));
 var viewModel = new List<AssignedCourseData>();
 foreach (var course in allCourses)
 {
 viewModel.Add(new AssignedCourseData
 {
198
 CourseID = course.CourseID,
 Title = course.Title,
 Assigned = instructorCourses.Contains(course.CourseID)
 });
 }
 ViewBag.Courses = viewModel;
}