'System' : a namespace with this name does not exist

c++ wpf build-error

Set Common Language RunTime Support to be "Common Language RunTime Support (/clr)" in 2 places in your project properties :

For Visual Studio before 2019:

For Visual Studio 2019:

c++ wpf build-error

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:

CodeHunter