private void handleChevronMenuItemClick( object sender, EventArgs e ) {
if ( sender == null ) return;
if ( !(sender is MenuItem) ) return;
MenuItem menu = (MenuItem)sender;
if ( menu.Tag == null ) return;
if ( !(menu.Tag is ToolBarButton) ) return;
ToolBarButton button = (ToolBarButton)menu.Tag;
ToolBar parent = button.Parent;
Rectangle rc = button.Rectangle;
uint lparam = (uint)win32.MAKELONG( rc.Left + rc.Width / 2, rc.Top + rc.Height / 2 );
win32.SendMessage(
parent.Handle,
win32.WM_LBUTTONDOWN,
win32.MK_LBUTTON,
lparam );
win32.SendMessage(
parent.Handle,
win32.WM_LBUTTONUP,
win32.MK_LBUTTON,
lparam );
}