ASP powered CSS file and bundling

Question

For a while now I have adopted the practice of writing my CSS in an .aspx page and serving that page as CSS. Primarily this is because a project I was involved on had a development 'CDN' before images were finally hosted on the actual CDN, so when it came to background images I needed a way of changing the URL through the web.config. I also get a few other perks like variables. A small sample:

#id
{
    color: '<%= PrimaryColor %>';
    background-image: url('<%= PrependCdnUrl("myimage.jpg") %>');
}

Since working on an MVC project I'd now like to incorporate CSS bundling into the original project (a webforms project). The problem I have, an .aspx page is not allowed to be bundled up, I get errors similar to:

(1,1): run-time error CSS1019: Unexpected token, found '<'
(1,2): run-time error CSS1019: Unexpected token, found '%'
...

Does anyone know how I could get this to work?

Answer 1

Short answer: It is not possible.

Long answer: It is possible through some hacks.

Actually there are 2 possibilities that pop into my mind that would accomplish this (they are not tested, not sure if they work out finally tough):

• In your IIS you can define which filetype gets handled by which interpreter. You can try to define .css files to use the same interpreter as ASP.NET pages. (not sure if this works)
• You can create an .aspx file instead of a .css file where you output the css code you need dynamically. Set the MIME type of the return stream from this dynamic css aspx page to the MIME type of CSS. Then reference your aspx page as css file