'System' : a namespace with this name does not exist
Set Common Language RunTime Support to be "Common Language RunTime Support (/clr)" in 2 places in your project properties :
For Visual Studio before 2019:
- Configuration Properties -> General
- Configuration Properties -> C/C++ -> General
For Visual Studio 2019:
- Configuration Properties -> Advanced -> C++/CLI Properties
- Configuration Properties -> C/C++ -> General
It was not enough for me when I just changed "Common Language RunTime Support (/ clr)".
I had to create the project in VS which would be a dedicated project for CLR:
If you cannot see this option, you should add it in the VS installer first:
Mif's answer was a little incomplete for me. If you still have the issue, you'd might want to check if you set the correct C++-version.
For me it specifically needed ISO C++17 because the VS default preset ISO C++14 (at least a preset in my version) does not support the required CLI-packages. Thus, still set the Runtime support to Common Language RunTime Support (/clr) and set the correct C++ Language Standard in the Configuration Properties -> General tab.
Note: As of now (October 2021) ISO C++20 is currently not supported in CLI and will also fail to find System - I only found the 17-version to be compatible.
Since its a little easer the visual way, here the screenshots. And also don't forget Yinon_90's hint to have the version as well as dependencies installed!
