How to change the Master Page dynamically

Question

I want to assign one master page dynamically for a pure aspx file, Anybody can tell me, how to do this?

Answer 1

I Left the ContentPlaceholder to add on it.. Actually , I tried to assign master page without using ContentPlaceHolder.. Now, I realised that, atleast one ContentPlaceholder should be there temporarily, even though we will change the master page dynamically...