Since last week I was trying to fix one following issue coming whenever I ran my any of .Net Core API and Web project.
My Visual Studio 2017 was showing “Start” option only. After numerous try I found one very helpful blog here which solved my issue.
In Visual Studio go to Tools -> Extensions and Updates I disabled the “Arduino GDB for Visual Micro 2017” extension.
In my case “Arduino GDB for Visual Micro 2017” was causing the issue. If you are not using it then you may try some other available options.