Devexpress tabheader disappears

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C#

WinForms

DevExpress

I have created ribbon form (XtraMain)and I set IsMdiContainer Property to true,i also add documentManager controle i set MdiParent to XtraMain I have add this code to open child forms

public void ViewChildForm(XtraForm _form)
        {
            if (!IsFormActived(_form))
            {
                _form.MdiParent = this;
                _form.Show();
            }

        }
      private bool IsFormActived(XtraForm form)
        {
            bool IsOpenend = false;
            if (MdiChildren.Count() > 0)
            {
                foreach (var item in MdiChildren)
                {
                    if (form.Name == item.Name)
                    {

                        tabbedView1.ActivateDocument(item);
                        IsOpenend = true;
                    }

                }
            }
            return IsOpenend;
        }

and i use this code in click of button to open the child form

private void bbtnEmployee_ItemClick(object sender, ItemClickEventArgs e)
        {
            FrmEmployee frme = new FrmEmployee();
            frme.Name = "FrmEmployee";
            ViewChildForm(frme);
        }

my problem start when the form contain a LayoutControl for example i have this code that open on click of button

private void btnBonLivraison_ItemClick(object sender, DevExpress.XtraBars.ItemClickEventArgs e)
        {
            LayoutControl lc = new LayoutControl();
            lc.Dock = DockStyle.Top;
            LookUpEdit OrderNumber = new LookUpEdit();
            OrderNumber.Properties.TextEditStyle = TextEditStyles.DisableTextEditor;
            OrderNumber.Properties.DataSource = shippProdu.GetOrderNumber();
            OrderNumber.Properties.DisplayMember = "N° Bon de livraison";
            OrderNumber.Properties.ValueMember = "N° Bon de livraison";
            lc.AddItem(Resources.selectOrderNumber, OrderNumber).TextVisible = true;
            lc.Height = 70;
            this.Controls.Add(lc);
            this.Dock = DockStyle.Top;
            lc.BestFit();

the second I click on a button the tabHeader disappears,what cause this problem?and how can I solve it.before I use documentManager I used XtraTabControl and if i click a button to open LayoutControl and after that try to open another form the focus remaining in the first form even when the form two is already opened and if I want to go to form two I must first click on a tab of the first form and then click on tab of the second form , thanks in advance .
this is my main form
https://i.stack.imgur.com/Ab9CN.jpg[^]
and this is when the TabHeader disappears
https://i.stack.imgur.com/tP92N.jpg[^]

What I have tried:

I try to use a separate UserControl with DocumentManager but did not work form me.