Weird bug/feature in Visual Studio 2010

As I was working with some of my demo code for the Azure posts I have been putting up lately, I came across a very odd thing. I had a solution with several projects that built and worked perfectly fine. I did however need to make some changes to the solution before zipping it up and putting it on my blog. So I made a copy of the solution folder, removed my source control bindings and everything else that shouldn’t be in the zip.

Before zipping it up, I thought I would just make sure it built ok after my changes, which it obviously should as I made no code changes. So I loaded the solution into Visual Studio and everything looked fine. But pressing Ctrl+Shift+B made Visual Studio cough and tell me that XXX was not available in namespace YYY, which is really odd as I had made no code changes.