Writing shorcode in widget does not show anything? By default the widgets does not have the support for the shortcodes or php. You have to manually enable the support for the shortcodes in widget area under text widgets. Some theme might have the support for shortcodes in widget area.
To enable shortcode in widgets just copy the following code snippet in your function.php file.
// Enable shortcodes in widgets add_filter('widget_text', 'do_shortcode');