When debugging ASP.NET MVC app, breakpoints are not hit

Question

When trying to debug a ASP.NET MVC app, the breakpoints in my controllers arent getting hit. When entering debug mode they just show an empty red circle with a warning trian

Answer 1

Some team member deleted the Debug configuration for one project (The MVC Project). Though the Solution configuration was set to "Debug / AnyCPU", if you looked in the configuration for that, the Project-Configuration for the MVC Project was set to Release, with no option for Debug, and all other projects were set as Debug appropriately.

So I added Debug back to the project configurations (Just drop-down "Add"... uncheck the box to add to solution). And viola...