If you get the above error when trying to add a WCF service reference that you have previously deleted then try:

  • deleting the Service References.DeviceService.Reference.cs.dll file you'll find under obj\Debug\TempPE. 
  • deleting the service folder you'll still find under Service References on disk, even though you deleted the reference in Visual Studio.
  • commenting out all references to the service's namespace in your code
  • rebuilding