So I’m trying to create an MVC3 web app. I decided to use EF taking care of my database first, instead of using the code first or model first approach.
So, in terms of membership, is it good practice to use the auto-generated ASPNETDB.MDF going forward, and mapping my EF database to it? Or should I scrap it and add membership to my EF database?
The membership system is well known, tested, and functions well. You should use it, unless you have a good reason not to. Even then, you still should use the base IPrincipal and IIdentity functions that Membership and FormsAuth implement.