Explanation:

You got a task for working with ms sql database. You worked hard and finished the task in time. Now, the last step have to be done ... Publishing... yeah! Publishing your application. You need to bundle all the requierd files and applications with it (.NET Framework, SQL Server, Your References,... etc). You did that part also successfully.

Now, you want to test the published application right?. You installed it and when you run the application you got this error:

An attempt to attach an auto-named database for file C:\Documents and Settings\Administrator\My Documents\Visual Studio 2005\WebSites\WebSite1\App_Data\aspnetdb.mdf failed. A database with the same name exists, or specified file cannot be Opened, or it is located on UNC share.

Any idea what's happning?

There are several reasons for the above error. In most cases, it has nothing to do with the last part of the error message - "A database with the same name exists, or specified file cannot be Opened, or it is located on UNC share".

Here is some work arounds to get rid of the above error message:

1. Open SQL Server Management Studio and attach the .mdf file manually to the SQL Server. (Select the 'Databases' node, Right click and select 'Attach')

Now change your web.config and change the connection string to point to the pre attached database instead of auto attach.

2. SQLExpress creates a directory per user in "c:\Documents and Settings\[user name]\Local Settings\Application Data\Microsoft\Microsoft SQL Server Data\SQLEXPRESS" to store some information. Delete this directory and try again.

3. The windows account "ASPNET" must have write permission on the folder. If it is a Windows 2003 machine, provide write access to the account "NETWORK SERVICE" on the folder, instead of account ASPNET.

4. You may want to disable the "User Instance=true" and try.

5. Are you using beta versions of VWD, Visual Studio 2005 or SQL Server 2005 Express? Uninstall them and install the released versions.

6. User Instance=True will work only if your SQL Server 2005 Express is using Windows Authentication mode. It will fail if you are using mixed mode. (Select the computer name in the SQL Server Management Studio, right click and select 'Properties'. Select the node 'Security' to view/change the authentication mode)

7. Make sure your connection string is correct. It must be something like below:

"Data Source=.\SQLExpress;Persist Security Info=True;Integrated Security=SSPI;Initial Catalog=YourUserId_DatabaseName"

When you use Integrated Secuiryt=SSPI in the connection string, make sure you are using in the section of the web.config and also make sure to specify a valid windows account for the "Anonymous User" access section in IIS.