public void Add(CurveGraphModel model) { if (Items != null) { Items.Clear(); modelitems = null; } else { Items = new ObservableCollection <FrameworkElement>(); modelitems = new CurveGraphModel(); } modelitems = model; GraphGrid grid = DrawGrid.RenderGrid(model, camera); model.Item.Grid = grid; if (UpdateRender != null) { UpdateRender(this, EventArgs.Empty); } }