Add conditional stylesheet CSS for internet explorer only

Question

The following methods can be used to add CSS for specific versions of IE:

1. Paste the code into html.tpl.php:

   <!--[if lt IE 9]><link type="text/css" rel="stylesheet" src="/sites/all/themes/mytheme/less/ie.css"><![endif]-->

2. Make use of the plugin Conditional Styles

3. Use drupal_add_css() function

I have always used option #1 above, and adding yet another plugin for something so simple seemed crazy. BUT working with LESS and calling in statically means the file does not get processed by the LESS pre-processor, so the question:

How do you include a stylesheet using drupal_add_css() for specific versions of IE?

Answer 1

I Found the solution in the comments on the drupal documentation for drupal_add_css():

drupal_add_css(
  path_to_theme() . '/less/ie.less',
  array(
    'browsers' => array(
      'IE' => 'lte IE 9',
      '!IE' => FALSE
    )
  )
);

Using this resulted in the LESS file being compiled by the LESS pre-processor, and the style was included within <!--[if lte IE 9]> comment tags.