Today I was building a WCF sample, and suddenly I started getting a strange error: "The target assembly contains no service types. You may need to adjust the Code Access Security policy of this assembly.". Debugging worked, but it took a minute for Visual Studio to start debugging (and responding).

This used to be caused by a wrongly signed svcutil.exe in beta 2 (link) but this was not the case now.

At first I thought it had something to do with WCF configuration (I just made a couple of changes) but resetting didn't solve anything.

After a while it struck me, I had added a new Workflow Service project, which was incomplete (hence it couldn't find the service type). By unloading the project from the solution the problem went away.