connecting to sql express 2008 form visual c# 2008

Question

If i go to  database explorer in visual C# 2008 and click add i get the box called " choose data source" i select sql database file and click continue. next i browser for my mdf located at ( C:\Program Files\Microsoft SQL Server\MSSQL10.SQLEXPRESS\MSSQL\DATA\StatusChecker.mdf) and select it. then i hit test connection and i get database is in use.

I don't understand. All i want to do is just connect to my local SQLexpress and access that DB. It was easy with other versions of Visual studio. I know this being the express edition is limited but this is driving me crazy. How do i access my DB in SQL express? I don't have to use the wizard if someone want to show me the code to do it diagrammatically.