EF5 connection string error only in production - entity-framework

Question

When on my dev machine, all works perfectly. Even using production connection values (so even when I connect to production from the dev machine). I don't think it's a permission problem because I am using the same credentials, just using EF5 instead of linq2sql, as the previous version of the service that worked. Also, the sql-profiler does not show a failed login attempt.
Connection string is:
Data Source=MYSQLSERVER;Database=MYDB;Integrated Security=True;
The error is:
Invalid value for key 'attachdbfilename'.
I have logged the connection string being passed into the dbContext code:
Database.Connection.ConnectionString = settings.DbConnectionHourly;
This is a class that inherits from my real dbContext (which packaged in a dll) and the settings get injected. Again, this works in Dev but not in production (server 2008 r2, IIS 7.5, framework.4).

Answer 1

Turns out that entity framework was trying to be very smart, but it was giving a very un-smart error message. So by convention, if you don't pass the context name in as a constructor, entity framework will assume the classname as the name of the connection string. What it will also do (which I was unaware of), is in development it will automatically connect to and create a schema using the visual studio built in sqlExpress. So in development, everything worked because this 'automagic' creation succeeded and since I later changed the connection to a different database, I was none the wiser about what EF was doing under the covers (EF was doing the wrong things but the end result worked).
However, when the application went to production, there is no sqlexpress or any database on the webserver so the automagic connection/creation sequence failed. Now if the error message had any useful information in it, this would be obvious. But since I had never set an 'attachdbfilename', nor did it tell me what the value of 'attachdbfilename' was or any context or what it was trying to do, this made figuring this out that much more challenging.
The fix was simple:
public HourlyContext(ISettingsWrapper settings)
: base(settings.DbConnectionHourly)
{ }
Instead of setting the connection after the context gets created (the creation process will immediately try to work it's magic with it's built in conventions/defaults), I now set it immediately through the constructor.