SqlException: Login failed for user 'IIS APPPOOL\ASP.NET v4.0'

30 Jan 2011 13:55 wcf

I’m spiking a WCF service hosted in IIS this weekend. It uses SQL Server, and I was getting the following error in WCF Tracing:

Login failed for user 'IIS APPPOOL\ASP.NET v4.0'.

Fortunately, I quickly found this thread on the ASP.NET forums. To summarise:

On IIS 7 and later, don’t change it to use “NetworkService”.
In SQL Server, under Security / Logins, create the username exactly as displayed. You can’t search for it.
In SQL Server, under database / Security / Users, add the login as a user on your new database.

For the last part, you can add the login to the db_owner role during development, but you really ought to lock the permissions down properly (give SELECT / INSERT / etc. permissions as appropriate).