Say you are developing Project1. If you refer to stuff in a sister proj (Project “PROJA”) within the same solution, you must include PROJA in Project1’s References. You must see PROJA when you expand [1] Project1’s References list.
Now watch out. When you addReference -> Project, you may see PROJA. Now you must click OK. If you click Cancel, you will see PROJA not added to the References list.
[1] using that tiny “+” sign
