AvalonDock remove child in LayoutAnchorableGroup

Question

I'm creating LayoutAnchorable dynamically and adding it to a parent. A button fires this code and created layoutAnchrable, listbox and some content in it.

LayoutAnchorable layoutAnchorable = new LayoutAnchorable
        {
            Content = listBox,
            Title = _selectedSchema.Value,
            ContentId = _selectedSchema.Key,
            IsActive = true,
            IsSelected = true,
            CanFloat = true,
            CanAutoHide = false,
            CanClose = true,
            CanHide = false,
        };
        
        if(!panelXml.Children.Select(x => x.ContentId).Contains(layoutAnchorable.ContentId))
        {
            panelXml.Children.Add(layoutAnchorable);
        }
        else
        {
            panelXml.Children.Remove(layoutAnchorable);
        }

If there is the same layoutAnchorable in Children I want to remove it from the children list. I traced the code and it works just fine but panelXml.Children.Remove(layoutAnchorable); does not work.