Category Archives: MS SQL Server

Cannot attach the file ‘C:\…database.mdf’ as database x – Entity Framework

Hi everyone,

I ran into the following error when attempting to run ‘update-database’ on an initial migration:

Cannot attach the file ‘C:\Users\…\App_Data\aspnet-…115933.mdf’ as database ‘aspnet-…15933’

The solution to this one is pretty easy, remove the initial catalog property from your connection string.

…33.mdf;Initial Catalog=aspnet…

This is apparently caused by issues with EntityFramework and multiple projects in the same database. See the following stackoverflow answer for more info: https://stackoverflow.com/a/20176660/522859