Umbraco 7.2.8 - Macro caching with query string parameters

The following article written for an older version of Umbraco still works. Got an Umbraco 7.2.8 instance invalidating cache based on query string without any issue.

http://www.theoutfield.co.uk/blog/2011/02/caching-an-umbraco-macro-by-querystring-parameter

Thanks to the Author Matt for writing it up.