Is it possible to write a feature to inject a custom control into a masterpage?

Question

I have 3 site collections that need a specific css file, and to not have to make changes in multiple places our team has opted for a single masterpage. Instead of creating a second masterpage with a link to this css file, I was wondering if its possible to write a feature to add a user control that contains the css to the masterpage?

Answer 1

You can use delegate controls, check this article.