private void Hoadon_ClickHoaDon(string mahd)
{
this.Hide();
frmCTHD frm = new frmCTHD(int.Parse(mahd));
frm.ShowDialog();
this.Close();
}
private void btn_ThemHoaDon_Click(object sender, EventArgs e)
{
this.Hide();
hd.TaoHoaDon();
int mahdtam = hd.LayIDHoaDon();
frmCTHD frm = new frmCTHD(mahdtam);
frm.ShowDialog();
this.Close();
}