When I right click on Eval.svc within Visual Studio 2012 and view in browser, I get the following -
The type \'EvalServiceLibary.Eval\',
I just hit this issue myself, and neither this nor any of the other answers on the net solved my issue. For me it was a strange one whereby the virtual directory had been created on a different branch in another source control server (basically, we upgraded from TFS 2010 to 2013) and the solution somehow remembered it's mapping.
Anyway, I clicked the "Create Virtual Directory" button again, in the Properties of the Service project. It gave me a message about being mapped to a different folder and would I like to update it. I clicked yes, and that fixed the issue.