Its unlikely that any of our professional life projects have only one project in our solution, and likely that in every of our project we would have huge number of projects in it. It might get hectic for us to keep track of the projects and find it in a glance, moreover it not healthy for the project also.
Visual studio have a nice feature called “Solution Folder” which is a logical folder structure and does not have any physical existence in user’s disk. Bellow I have given a screen shot of one of my personal project, where I have categorized three part of my solution using solutions explorer.
In architecture I kept Business logic, data access layer and service layer. In infrastructure I kept helpers and business objects project and finally in UI solution folder I kept the web ui and window ui project. There could be more folder like this for instance “deployment” where all installer projects will go.
If solution folder had physical existence it would have been more helpful for us. But whatever we have serves our purpose.