One CSS per page in ASP.NET Theme

Question

Does anybody know how to do this?

Theme A
  style_for_x.aspx.css
  style_for_y.aspx.css
Theme B
  style_for_x.aspx.css
  style_for_y.aspx.css

Or even better:

Theme A
  style_for_all_pages.css
  style_for_x.aspx.css
  style_for_y.aspx.css
Theme B
  style_for_all_pages.css
  style_for_x.aspx.css
  style_for_y.aspx.css

Answer 1

The problem with ASP.NET themes is that all existing CSS files are included on every page.

Maybe you should move your CSS files to a different location (e.g. "~/css/ThemeA") and include them manually (or in a common base class for all of your pages) depending on the current page's name and the currently selected theme.