private void btnDangNhap_ItemClick(object sender, DevExpress.XtraBars.ItemClickEventArgs e)
{
CloseForm("Form9");
FormDangNhap f = new FormDangNhap();
f.MdiParent = this;
f.Show();
}
private void đăngNhậpToolStripMenuItem_Click(object sender, EventArgs e)
{
FormDangNhap formDangNhap = new FormDangNhap();
formDangNhap.Show(this);
}