dc=new SKSDataContext();
            var bild = dc.Builds.ToList();
            treeView1.ItemsSource = bild;

Build it = getElement(sender) as Build;
            var floorc = it.Floors.Count;
            Floor newfloor=new Floor();
            newfloor.ID_build = it.ID_Build;
            newfloor.Levels = (short) (floorc + 1);
            treeView1.ItemsSource = null;
            dc.Floors.InsertOnSubmit(newfloor);
            dc.SubmitChanges();
            treeView1.Items.Clear();
            treeView1.ItemsSource = dc.Builds.ToList();
            treeView1.Items.Refresh();