Add search to top bar

I have been trying to add a search option to the right hand side of the top bar without success, what is the easiest way of adding it?

I added the following code to css but it doesn’t appear to work.

add_filter(‘wp_nav_menu_items’, ‘add_search_form’, 10, 2);

function add_search_form($items, $args) {
if( $args->theme_location == ‘#top-bar’ )
$items .= ‘<li class=”search”><form role=”search” method=”get” id=”searchform” action=”‘.home_url( ‘/’ ).'”></form>’;
return $items;
}