private void dtk_btn_Click(object sender, EventArgs e)
        {
            this.Hide();
            irdtkInput i = new irdtkInput();

            i.Show();
        }
        private void dangkyBtn_Click(object sender, EventArgs e)
        {
            try
            {
                DANGKYTHICCQT_KHAC();
            }
            catch
            {
                MessageBox.Show("Lỗi nhập liệu");
                irdtkInput i = new irdtkInput();
                i.Show();
                this.Hide();
                return;
            }

            PHIEUDUTHI p = new PHIEUDUTHI();

            p.Show();
            this.Hide();
        }