private void btnLapPhieuMoi_Click(object sender, EventArgs e)
        {
            i                      = 0;
            Tien                   = 0;
            txtTongtien.Text       = "0";
            btnLapPhieuMoi.Enabled = false;
            btnThemSP.Enabled      = true;
            cboNCC.Enabled         = false;
            btnIn.Enabled          = true;
            txtSoPĐ.Text           = DonDatHangBUS.GetIDPhieuDat();
            txtMaSP.ResetText();
            txtTenSP.ResetText();
            txtSoLuong.ResetText();
            txtGia.ResetText();
            dtkNgayDat.Value = DateTime.Now;
            dgvDanhSach.Rows.Clear();
            // Thêm vào auto complete.
            AutoCompleteStringCollection auto = new AutoCompleteStringCollection();

            foreach (DataRow row in SanPhamBUS.DanhSachSPTheoNCC(cboNCC.SelectedValue.ToString()).Rows)
            {
                auto.Add(row["MaSanPham"].ToString());
            }
            txtMaSP.AutoCompleteMode         = AutoCompleteMode.Suggest;
            txtMaSP.AutoCompleteSource       = AutoCompleteSource.CustomSource;
            txtMaSP.AutoCompleteCustomSource = auto;
        }