private void cboSearch_TextChanged(object sender, EventArgs e)
        {
            int i = 0;

            if (cboSearch.Text == "")
            {
                HienThiDanhSanhSachPhieuXuat();
                return;
            }
            px.Search = cboSearch.Text;
            List <PhieuXuatHang> pxlist = pxbll.TimKiemPhieuXuatHang(px);

            dgvPhieuXuat.Rows.Clear();

            foreach (PhieuXuatHang pxs in pxlist)
            {
                DataGridViewRow row = new DataGridViewRow();
                row.CreateCells(dgvPhieuXuat);
                row.Cells[0].Value = i + 1;
                row.Cells[1].Value = pxs.MaPx;
                row.Cells[2].Value = pxs.MaNv;
                row.Cells[3].Value = pxs.MaSp;
                row.Cells[4].Value = pxs.MaKh;
                row.Cells[5].Value = pxs.Slx;
                row.Cells[6].Value = pxs.NgayXuat;
                row.Cells[7].Value = pxs.PhanTram;
                row.Cells[8].Value = pxs.ThanhTiens;

                dgvPhieuXuat.Rows.Add(row);
                ++i;
            }
        }