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.

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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.