public void LoadDanhSachLop() { gcDanhSach.DataSource = null; gcDanhSach.Controls.Clear(); var dao = new LopDAO(); var lst = new List <Lop>(); var ids = string.Join(",", cbbDanhSachKhoa.Properties.Items.GetCheckedValues()); var ser = txtSearch.Text; if (string.IsNullOrEmpty(ids)) { lst = dao.GetAll(ser); } else { lst = dao.GetAllByMaKhoa(ids, ser); } gcDanhSach.DataSource = lst; }