DockingPane in MDI Child Form :NET Dessapear

/// <summary>
/// Creates a DockingPaneManager object
/// </summary>
/// <param name="frm"></param>
/// <returns></returns>
public static AxXtremeDockingPane.AxDockingPane DockingPaneManager(Form frm)
{
    AxXtremeDockingPane.AxDockingPane DockingPaneManager = new AxXtremeDockingPane.AxDockingPane();
    ((System.ComponentModel.ISupportInitialize)(DockingPaneManager)).BeginInit();
    frm.SuspendLayout();

    DockingPaneManager.Enabled = true;
    DockingPaneManager.Location = new System.Drawing.Point(21, 12);
    DockingPaneManager.Name = "DockingPaneManager";
    DockingPaneManager.Size = new System.Drawing.Size(24, 24);
    DockingPaneManager.TabIndex = 0;

    frm.Controls.Add(DockingPaneManager);
    ((System.ComponentModel.ISupportInitialize)(DockingPaneManager)).EndInit();
    frm.ResumeLayout(false);

    DockingPaneManager.AttachToWindow(frm.Handle.ToInt32());
    DockingPaneManager.VisualTheme = XtremeDockingPane.VisualTheme.ThemeResource;
    DockingPaneManager.Options.HideClient = true;
    DockingPaneManager.PaintManager.HighlightActiveCaption = false;
    DockingPaneManager.PaintManager.SplitterStyle = XtremeDockingPane.DockingPaneSplitterStyle.PaneSplitterSoft3D;
    DockingPaneManager.PanelPaintManager.Layout = XtremeDockingPane.XTPTabLayoutStyle.xtpTabLayoutAutoSize;
    DockingPaneManager.SendToBack();

    return DockingPaneManager;
}

// Create a global DockingPaneManager variable
private AxXtremeDockingPane.AxDockingPane DockingPaneManager;

//In the load event, create the object and use as you would have in VB6.
DockingPaneManager = BSDLibrary.Codejock.DockingPaneManager(Instance);