I installed LocalDb using the SqlLocalDb.msi package and I can connect to it using SSMS using the server name (LocalDb)\v11.0. So far so good. The problem is that when I try to connect to it via a .NET 4.5 application I get the error
The server was not found or was not accessible.
I started with the connection string Data Source=(LocalDb)\v11.0 and then added many things to no avail (integrated security true/sspi, attaching a db, using instances, etc.)
I think you hit the same issue as discussed in this post. You forgot to escape your \ character.