private void btDanhmuc_Click(object sender, EventArgs e)
        {
            DanhMuc_Form frm = new DanhMuc_Form();

            frm.ShowDialog();
        }
 private void btDanhmuc_Click(object sender, EventArgs e)
 {
     DanhMuc_Form frm = new DanhMuc_Form();
     frm.ShowDialog();
 }