Having been in the development game for almost 20 years, this chestnut has continued to plague me across multiple projects.
As such, today whilst experiencing this same problem again, against another project, I decided to investigate further and I do believe this is related to Bin folder location... or more specifically, the output path of the bin folder.
For me, for a simple service based web application configured to run/debug through IIS, it was changing the output path from bin\debug to bin\ that resolved it
Project > Properties > Build > Output path
Seriously hopes this helps.