'System' : a namespace with this name does not exist
Solution 1
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
Solution 2
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:
Solution 3
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!
![Narendra](https://i.stack.imgur.com/REAO6.jpg?s=256&g=1)
Narendra
I am a .net, C++ developer for more than 6 years. I have cleared MCTS 70-515 certification. I am interested in playing computer games(mainly racing). I also like photography. Currently I am working in WPF and C++. http://narendra-mallik.branded.me/
Updated on July 09, 2022Comments
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Narendra almost 2 years
I had a C++ project which was running perfectly. Now I copied the project to another folder and added the project to a WPF application solution.
Now the C++ project is giving me lot of build errors. One of them is
"System' : a namespace with this name does not exist"
.Below are the lines which creates this error.
#include "stdafx.h" using namespace System; using namespace System::Reflection; using namespace System::Runtime::CompilerServices; using namespace System::Runtime::InteropServices; using namespace System::Security::Permissions;
The above lines are in AssemblyInfo.cpp file. I don't have any experience of C++, so finding it difficult to remove the errors. Any help is appreciated. Below is another error which might be helpful for you to resolve the issue.
managed targeted code requires a '/clr' option
Thanks in advance.