Visual Studio couldn't find UGameplayStatics

I’m trying to use VS2017 with UE4, but it seems a lot of classes couldn’t be found by VS. One in particular is UGameplayStatics.

If you type UGameplayStatics with Visual Assist installed, it will find the class, but without VAX, it just couldn’t.

Is VS2017 fully supported by UE4 without Visual Assist or is it practically mandatory?

Are you including the proper header? #include "Kismet/GameplayStatics.h"