private void btnMatHang_Click(object sender, EventArgs e)
 {
     FrmMatHang frm = new FrmMatHang();
     CreateTab(stcMenu, "Mặt Hàng", "stiMatHang", "stcpMatHang", frm);
 }
        private void btnMatHang_Click(object sender, EventArgs e)
        {
            FrmMatHang frm = new FrmMatHang();

            CreateTab(stcMenu, "Mặt Hàng", "stiMatHang", "stcpMatHang", frm);
        }