What is the best/cleanest way to implement A-B testing in asp.net mvc?

What is the best and cleanest way to implement A-B testing in asp.net mvc? That is, when we make new changes to an asp.net mvc web site, we want to test the new html/css/js with a certain subset of visitors (defined on cookie, login id, etc) and then analyze some metrics (page response time, number of pages visited, $$$ in sales, etc) afterwards to measure the level of success of the changes.

I am looking for a clean way to implement a way of choosing what view (html/css/js, etc...) to render using asp.net mvc.