Unable to start debugging. The startup project could not be launched. VS2015

Question

I have started a new console project in VS2015. I only have this code :

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text         


        

Answer 1

VS 2019, two Core 3.1 projects (an MVC and an API), brand new projects created, no other changes to the solution or projects.

I kept getting the referenced error when trying to start both projects within the IDE, despite having checked all the things already mentioned in this SO.

However, I finally realized, I forgot to specify the "Action" after switching the solution to "Multiple startup projects" (they were both still set to "None"). Right-click solution in "Solution Explorer", choose "Properties" (at very bottom).

Such a ridiculously simple thing. Hope it helps someone else.

"Broken"

Working