private void đăngKíToolStripMenuItem_Click(object sender, EventArgs e)
        {
            this.Hide();
            Form_dangki dki = new Form_dangki();

            dki.Show();
        }
        private void labelDangki_Click(object sender, EventArgs e)
        {
            this.Hide();
            Form_dangki dk = new Form_dangki();

            dk.Show();
        }