I have 2 project and one project uses the other project(which is a framework that all my projects are going to use). I can't seem to find a way to include those file for auto-complete/intellisense, is there a way to do this and keep the other project(not the framework project) as the active project?

Right click on your active project (not the framework), then click "Properties" and checkout the last entry on the "Properties" tab page.
"Code insight includes" allows you to specify directories to parse for intellisense usage