private void toolBarMain_Loaded(object sender, RoutedEventArgs e)
        {
            ToolBar toolBar = sender as ToolBar;
            var overflowGrid = toolBar.Template.FindName("OverflowGrid", toolBar) as FrameworkElement;
            if (overflowGrid != null)
            {
                overflowGrid.Visibility = Visibility.Collapsed;
            }
        }