Build a Web Chat Application using ASP.Net 3.5, LINQ and AJAX (in C# 3

Introduction: A Java Programmer friend of mine once asked me if I have ever built a web chat application. I said "No". He then asked me if I were to build a really simple, monitored, bare minimum, working web chat application, how long do I think will it take (something to that effect). I said, "I don't know". A few days had passed, one lazy evening, I was surfing the web looking for ASP.Net web chat applications. It seems that I can't find one that is simple enough to implement. So I decided to just build something simple from scratch. When I say simple, that just means that: I'm am going to try to build this web chat as fast as possible, with very minimal planning or architecturing.