Modifing(adding a column to table) and reattaching database to .net project

I was working on a asp.net project when I realise I need to add a crucial column to my sql database. I understand VS2010 doesn't support adding columns hence I attached the database(I think it's created from SQL server 2005) to my SQL开发者_运维问答 server 2008 and add it, after which I detach the database and try to plug it back to my project but I am getting the '661 incompatibility error', I try to replicate the error again moments but I got instead:

"The file is in use. Enter a new name or close the file that's open in another program."

What is the correct procedure to modify my database tie to my asp.net project?

Thanks.

I'd say stop modifying databases directly in visual studio all together. Modify the database in SQL management studio and use a connection string in your web.config file to connect to the database. It's the cleaner and I believe logical choice.