In Visual Studio 2013 Ultimate with a CS file open within a Class project, the project name appears as "(Miscellaneous Files)".
This Class project was a mixture of .CS files and Xaml workflow files.
- I selected all the Xaml files and right clicked them and choose "Exclude From Project"
- I selected "Show All Files" in Solution Explorer for the project
- I selected all the Xaml files I had originally excluded and right clicked them and choose "Include In Project"
Re-open a .CS file and see if the project drop down lists "(Miscellaneous Files)"