private void LoadAssignedList()
        {
            using (var helper = new DbHelper.Subject())
            {
                var assignedCourses = helper.ListCoursesOfStructure(YearId, SubYearId);
                //ViewState["SavedCourses"] = assignedCourses;

                foreach (var subject in assignedCourses)
                {
                    lstAssignedCourses.Items.Add(new ListItem()
                    {
                        Value = subject.Id + "_" + subject.CategoryId + "_" + subject.Credit + "_" + subject.IsElective.ToString(),
                        Text  = subject.Name
                    });
                }
            }
        }