adding custom style to wp-admin wordpress

gistfile1.php

   <?php
      //http://wordpress.stackexchange.com/questions/110895/adding-custom-stylesheet-to-wp-admin
      //from functions.php

      //First solution : one file
      add_action( 'admin_enqueue_scripts', 'load_admin_style' );
      function load_admin_style() {
        wp_register_style( 'admin_css', get_template_directory_uri() . '/admin-style.css', false, '1.0.0' );
//OR
        wp_enqueue_style( 'admin_css', get_template_directory_uri() . '/admin-style.css', false, '1.0.0' );
       }

      //Second solution : two or more files.
      add_action( 'admin_enqueue_scripts', 'load_admin_styles' );
      function load_admin_styles() {
        wp_enqueue_style( 'admin_css_foo', get_template_directory_uri() . '/admin-style-foo.css', false, '1.0.0' );
        wp_enqueue_style( 'admin_css_bar', get_template_directory_uri() . '/admin-style-bar.css', false, '1.0.0' );
      }  

    ?>