private void bt_luu_Click(object sender, EventArgs e)
        {
            BenhNhan bn = new BenhNhan();

            bn.diachi = tf_diachi.Text;
            bn.hoten  = tf_hoten.Text;
            bn.msbn   = tf_msbn.Text;
            bn.socmnd = tf_socmnd.Text;
            ConnectDB.instance();

            if (BenhNhanDAO.InsertBenhNhan(bn))
            {
                SendText(bn);
                MessageBox.Show("Success");
                tf_diachi.Text = "";
                tf_hoten.Text  = "";
                tf_msbn.Text   = "";
                tf_socmnd.Text = "";
                tf_diachi.Focus();
            }
            else
            {
                if (tf_msbn != null)
                {
                    SendText(BenhNhanDAO.FindBenhNhanById(tf_msbn.Text));
                    MessageBox.Show("Success");
                }
                else if (tf_socmnd != null)
                {
                    SendText(BenhNhanDAO.FindBenhNhanByCMND(tf_socmnd.Text));
                    MessageBox.Show("Success");
                }
                else
                {
                    MessageBox.Show("Error");
                }
            }

            ConnectDB.disconnect();
            Console.WriteLine("send oke");
            Console.ReadLine();
        }