private void Lecturer_Page_Loaded(object sender, RoutedEventArgs e) { _lecturerViewModel = new LecturerViewModel(); _centerViewModel = new CenterViewModel(); _buildingViewModel = new BuildingViewModel(); _facultyViewModel = new FacultyViewModel(); _departmentViewModel = new DepartmentViewModel(); List <LecturerEntity> lecturers = _lecturerViewModel.LoadLecturerData(); lecturer_data_grid.ItemsSource = lecturers; center_combobx.ItemsSource = _centerViewModel.LoadCenterData(); building_combobx.ItemsSource = _buildingViewModel.LoadBuildingData(); faculty_combobx.ItemsSource = _facultyViewModel.LoadFacultyData(); department_combobx.ItemsSource = _departmentViewModel.LoadDepartmentData(); foreach (LecturerEntity l in lecturers) { lecturerIds.Add(l.EmployeeId); } add_btn_.IsEnabled = false; update_btn_.IsEnabled = false; delete_btn_.IsEnabled = false; emp_id_txtbx.Text = "Eg: 000150"; }