private void UpdateForm()
{
var oldStudent = _studentForm.GetStudent();
var updatedStudent = _studentBll.GetStudent(oldStudent);
_studentForm.LoadStudent(updatedStudent);
_studentForm.LoadEnrolledCourses(updatedStudent.Courses.ToList());
var availableCourses = _courseBll.GetCourses();
foreach (var course in updatedStudent.Courses)
{
availableCourses.Remove(course);
}
_studentForm.LoadAvailableCourses(availableCourses);
_studentForm.LoadStudentGrades(updatedStudent.Grades.ToList());
}