In school I had to make a basic website in Dreamweaver (just a few pages and a stylesheet), at the beginning of the year. At the end of the year, my teacher got us to reconstruct that website in Microsoft Visual Web Developer.

Now I was wondering if there are any benefits of doing this in the "real world" (converting a HTML/CSS website into ASP.Net).

If you had any server side code then yes, if they were static pages with no dynamic content, then no.

yes for dynamic page

Look here http://www.objectisnull.com and good luck.