Cannot add reference to C++ dll project

Question

Hi,

I have a WPF desktop bridge solution (VS 2017). In the main project (WPF app in C#) I could add a reference to a C++/CLR project. Now I created a C++ dll project without CLR support. In it I use functions from the namespace Microsoft::WRL and it's not allowed to use this namespace in a dll with CLR support. I set the project dependencies and want to add the C++ dll project to the references of the main project. But I get the following error:

Why is it? What can I do?

Answer 1

Hi,@Heiko. Welcome Microsoft Q&A.

The error message A reference to '*' could not be added. The method or operation is not implemented" usually indicates a problem with the project reference you are trying to add.

Here are some things you could try to fix this problem:

1. Check the path to the C++ project: Make sure the path to the C++ project is correct and exists. If the path is incorrect or the project does not exist, the reference will not be added.
2. Check your Visual Studio version: Make sure you are using a version of Visual Studio that supports adding C++ project references. Not all versions of Visual Studio support this feature.
3. Check C++ project compatibility: Make sure your C++ project is compatible with the .NET Framework version used in your WPF project. If the C++ project is not compatible, you will not be able to add references.
4. Try adding references manually: Instead of using the Add Reference dialog, try adding references manually by editing the .csproj file. You can do this by opening the .csproj file in a text editor and adding a reference to the C++ project. Here's an example of what a reference might look like:

<ProjectReference Include="[path to your C++ project .vcxproj file]">
  <Project>{[C++ project GUID]}</Project>
  <Name>[C++ project name]</Name>
</ProjectReference>

Make sure to replace the path and GUID with the correct values for your C++ project.

5.Restart Visual Studio: Sometimes simply restarting Visual Studio resolves issues with adding project references.

You can also try to see if the solution here helps you.

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