private void btnLapHoaDonMoi_Click(object sender, EventArgs e)
{
i = 0;
Tien = 0;
txtTongtien.Text = "0";
btnLapHoaDonMoi.Enabled = false;
btnThemSP.Enabled = false;
pbcheck.Enabled = true;
btnIn.Enabled = true;
txtMaKH.ReadOnly = false;
txtSoHD.Text = HoaDonBanHangBUS.GetIDHoaDon();
txtMaSP.ResetText();
txtTenSP.ResetText();
txtGiamGia.ResetText();
txtGiaBan.ResetText();
txtMaKH.ResetText();
dtkNgayLap.Value = DateTime.Now;
dgvDanhSach.Rows.Clear();
}