Visual Studio 2010 Express not finding classes in namespace via Intellisense or class view

I had a project I wanted to resurrect from years past and get moving again. I had various class files already developed in VS Express 2008 already written. I created a new .NET Web Application Project using 4.0. I copied my files into a new App_Code folder and then added them to the project via the solution explorer and didn't think anything of it. After spending some time building my site framework, I started in on the code behind of one of the pages and when I went to reference a class file, it wouldn't appear in the Intellisense. I confirmed it was the same namespace as the page I was working on and tried again, still nothing.  I checked class view and all the classes I had imported were missing, but they all had the same namespace as well.  Finally, to check my own sanity, I created a new class in the project but now even that doesn't show up in class view or Intellisense.  

These are all just straight up code *.cs files, nothing is compiled, no DLL reference and every file uses the same namespace. Am I missing a step (prayer beads? mystic? voodoo chant?) to get these properly imported and functional in my project? Should I not use the App_Code folder? I'm dead in the water!