Visual Studio 2017 warning errors when starting a debugger for multiple Visual Studio 2012 C# projects in a solution

Question

I am using Visual Studio 2017 Professional 15.5.5 for building and debugging a project of Visual Studio 2012. When I start a debugger for an executable file, I see following warning messages on multiple projects of C# in the solution:

A problem occurred while trying to set the "References" parameter for the IDE's in-process compiler. Sequence contains more than one matching element

Is there any way to fix this issue?

Update: cleaning up the source tree fixed this issue, but the root cause was not found.

Answer 1

Try checking to see if there is a app.config file in the .csproj file section. Removing it from the solution explorer could fix the problem