/// <summary>
        ///
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void frmNguoiDung_Load(object sender, EventArgs e)
        {
            if (this.Controller == null)
            {
                this.Controller = new NguoiDungController();
            }
            //Hien thi combobox loai nguoi dung
            LoaiNguoiDungController ctrlLoaiNguoiDung = new LoaiNguoiDungController();

            ctrlLoaiNguoiDung.HienThiComboBox(this.cmbLoaiNguoiDung);
            ctrlLoaiNguoiDung.HienThiDataGridViewComboBoxColumn(this.colLoaiNguoiDung);

            //Hien thi combox giao vien
            GiaoVienController ctrlGiaoVien = new GiaoVienController();

            ctrlGiaoVien.HienThiComboBox(this.cmbGiaoVien);
            //Them mot dong co ma giao vien la null de khi chon loai nguoi dung k phai la  giao vien
            DataRow row = ctrlGiaoVien.Data.DataService.NewRow();

            row["MaGiaoVien"] = DBNull.Value;
            row["HoTen"]      = "Khác...";
            ctrlGiaoVien.Data.DataService.Rows.Add(row);

            //An combobox giao vien
            this.lbGiaoVien.Visible  = false;
            this.cmbGiaoVien.Visible = false;

            //Dat vi tri combobox giao vien trung voi ten nguoi dung
            this.lbGiaoVien.Location  = this.lbTenNguoiDung.Location;
            this.cmbGiaoVien.Location = this.txtTenNguoiDung.Location;

            this.Controller.HienThiDS(this.dgvDS, this.bnDS, this.txtTenDangNhap, this.txtMatKhau, this.cmbLoaiNguoiDung, this.txtTenNguoiDung, this.cmbGiaoVien);
        }