How to get the file extension from a url?

Question

New to ruby, how would I get the file extension from a url like:

http://www.example.com/asdf123.gif

Also, how would I format this string, in c#

Answer 1

This works for files with query string

file = 'http://recyclewearfashion.com/stylesheets/page_css/page_css_4f308c6b1c83bb62e600001d.css?1343074150'
File.extname(URI.parse(file).path) # => '.css'

also returns "" if file has no extension