void RefeshForm() { txtMaNL.Text = NguyenLieuBUS.LayMaNLLonNhat(); txtTenNL.Clear(); txtDonGia.Clear(); txtSLTonKho.Clear(); cboDonViTinh.SelectedValue = -1; cboLoaiNL.SelectedValue = -1; cboNhaCC.SelectedValue = -1; chkTrangThai.Checked = true; }