If anyone's still stuck on this, the easiest solution I found was to "Retarget Solution". In my case, the project was built of SDK 8.1, upgrading to VS2017 brought with it SDK 10.0.xxx.
To retarget solution: Project->Retarget Solution->"Select whichever SDK you have installed"->OK
From there on you can simply build/debug your solution. Hope it helps