Adding a new project to an existing solution in TFS

The problem is the solution has lost its binding. That's why it's not checking out automatically when you add the new project.

In order to restore the binding in VS 2010, go to File->Source Control->Change Source Control. Look for the "Solution: your solution name" and if it's not bound it will say "no server". Click on it and then click "Bind" from the toolbar.

in Visual Studio 2012/2013 it's File->Source Control->Advanced->Change Source Control (Thanks to danglund).

This should create a new vssscc file that is correctly bound. Now add the new project and everything should work correctly.

I was also having the same problem, this is how I fixed it:

Go to Visual Studion: File->Source Control->Change Source Control Find your project there, its status would be "Invalid", Click on it and press "Unbind". Now go back to Solution Explorer and Remove your project. Add this project again into the solution explorer solve the problem.

Good Luck!