>I don't understand why the Customer project needs an entry point. The solution will be compiled into an EXE, who's startup project is AppShell. I don't need a form in the Customer project (yet). I will be creating tabs classes that will appear on the AppShell desktop form in the first project.
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When you created the Customer project you probably selected "Windows Forms Application". That basically means it's going to compile to an EXE, and as such requires an entry point. What you probably wanted to do was create a new project using the "Class Library" template instead - you can add any kind of item you want to the project itself (eg. forms, for example).