IntelliSense: "#using" requires C++/CLI to be enabled
Your project settings are wrong. Specifically Configuration Properties, General, Common Language Runtime support.
Fall in the pit of success by starting your project by picking one of the project templates in the CLR node.
Choose Project
-> Properties
from the menu bar. In the Project properties
window, under Configuration Properties
-> General
, make sure that Common Language Runtime Support
is set to Common Language Runtime Support (/clr)
In VS2019 it the steps would be :
1/ Right click on the project
2/
Project
3/
Properties
4/
Configuration Properties
5/
Advanced
6/
Common Language Runtime Support
change it toCommon Language Runtime Support(/clr)