[ADO.NET] System.Data.SqlClient.SqlException: Failed to generate a user instance of SQL Server due to a failure in starting the process for the user instance. The connection will be closed.

Question

Anybody ever get this error and/or have any idea on it's cause and/or solution?

I'm asking this on behalf of a friend but there is info at http://forums.microsoft.com/MSDN/ShowPost.aspx?PostID=125227&SiteID=1

Update

The connection string is "=.\SQLEXPRESS;AttachDbFilename=C:\temp\HelloWorldTest.mdf;Integrated Security=True"

I suggested the "User Instance=false". That works for him.

Answer 1

Can you list the connection string you are using for this?

You might want to try adding an explicit User Instance=true/false to your connection string

Answer 2

Are you using SQL Express? Is the SQL Server on a local box or is it on a server, and if so are you using terminal services to connect to it?

Couple of links that might help:

• http://forums.microsoft.com/msdn/showpost.aspx?postid=98346&siteid=1
• http://snipr.com/3hat2

Answer 3

"User Instance = false" worked.

@jon Thanks for commenting, though I had suggested that already based on the MSDN forum post linked above. I'll give you the accept answer until they fix http://stackoverflow.uservoice.com/pages/general/suggestions/17789 .

Answer 4

Here is the answer to your problem:

Very often old user instance creates some temp files that prevent a new SQL Express user instance to be created. When those files are deleted everything start working properly. Check detailed info in the this article:

Fix error "Failed to generate a user instance of SQL Server due to a failure in starting the process for the user instance."