private void UpdateUI() {
            Layer layer = GetSelectedLayer();
            if (layer != null) {
                layerProperties.SelectedObject = layer;
            }
            btnAdd.Enabled = KbgeLeApp.Get().GetSelectedLevel() != null;
            btnRemove.Enabled = (layer != null);
            btnDown.Enabled = (layer != null && lstLayers.SelectedIndex != (lstLayers.Items.Count - 1));
            btnUp.Enabled = (layer != null && lstLayers.SelectedIndex != 0);
            layerProperties.Enabled = (layer != null);
        }