User-718146471 posted
Take a look at this thread: http://forums.asp.net/t/1030595.aspx
Then for the membership inside your application you don't need to use the database, but depending on your AD, you may need to use your own set of roles for the application, which can reside in the database, or in an xml file or whatever.
You may also implement other providers that need a data store, as in profile, or personalization. If you choose to have these use your mdf file, that is completely your business. Do you need these and if so, where are you going to store that
information. It all depends on what your web application requires.
Ted