ASP.NET site with multiple DLLs

A client has a website, needs a few extra pages, but does not have the source code for the original site.

My first thought is to create a new solution with the new开发者_如何学编程 pages, compile them to create as a DLL and then copy the pages and the new DLL to the server. I'm not sure if this will work for the simple reason that I've never had to do it, but it seems quite logical. Is there anything that I'm missing?