Embedded SQL Server Express Deployment - Unhandled Exception: Database already exists

Good Afternoon.

I am trying to write a short application within which I would like to embed a SQL Server Express database, all of which would be deployed via ClickOnce through a web site. The installation process seems to be working without trouble, including installation of the .NET Framework 2.0 and SQL Server Express 2005.

When the application launches on the new machine, however, I get a big Microsoft .NET Framework "Unhandled exception" error dialog box that indicates the database already exists and that the database file could not be attached. I am working with a clean virtual machine that I know has never had the database installed on it.

I fear I am overlooking something quite straightforward, but since this is the first time I have ever attempted to build a data-bound application, I am not sure where I am going wrong.

Perhaps the source of the problem, or a related problem, might be revealed even when I run the application in debug mode from within Visual Studio. I can run the application once, but if I try to run it again, I get an error when I try to open the database connection that is similar in content (database already exists...could not attach). I can run the SSEUtil and detach the database and then run the application again in debug mode and it works no problem (the first time!).

Lastly, if I install the application on the machine on which it was developed and make sure the database is detached, it will run without any trouble (even repeatedly). But, on a new blank machine, there is no database listed that matches my database name, so I cannot try to detach anything!?

My apologies for such a novice question!

Sean

Hi Sean,

I would suggest removing the ‘Initial Catalog’ keyword from your connection string. Among the things that are stored about a database when it is attached is the Name/Path pairing; SQL Server gets a little upset if you try to attach a database using an existing name but with a different path. Enter the |DataDirectory| macro…

I’m guessing you’re using ClickOnce deployment for this application. There are things that will cause the install directory of a ClickOnce deployment to move, when this happens, VS magically fixes up things as far as the application goes, but it cannot fix up the fact that SQL Server has recorded your explicit database as being linked to the old file location. When you attempt to open the application now, the attach fails because there is already a database named JMU_2007 listed in the master database, but it is associated with a different path, so you get the error that the database already exists. I’m guessing this is the problem you’re hitting.

By removing the ‘Initial Catalog’ keyword, you’re forcing SQL Express to give the database an autoname based on its path. If the database moves as a result of VS behavior, the name will be changed because the path has changed, so it will appear to be a different database from the SQL perspective. Hopefully this helps.

Mike

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Thanks very much Mike. That did the trick...I can't believe I overlooked that after spending too much time trying to fix this problem.

Sean