When a user registers with my site, they will get a url like this \"http://username.mysite.com\" to access their page/folder. How this is possible using C# and asp.net mvc.<
Rather than have the username as a subdomain how about having it as part of the URL path. Would be a lot easier for you to implement.
www.mysite.com/users/ravi www.mysite.com/ravi
Then you could tailor your View page dependent on the username.