private void tổngQuanToolStripMenuItem_Click(object sender, EventArgs e)
        {
            TongQuan tq = new TongQuan();

            tq.MdiParent = this;
            tq.Show();
        }
        private void Trangchu_Load(object sender, EventArgs e)
        {
            Class.Function.Connect(); //Mở kết nối
            TongQuan tq = new TongQuan();

            tq.MdiParent = this;
            tq.Show();
        }