How do I add a reference to an unmanaged C++ project called by a C# project?

Question

One solution (the.sln)

One C++ project (mycppproject.vcxproj in 2010or mycppproject.vcproj in 2008) which compiles a native DLL exporting some function(s). In debug this builds c:outputDebugmycppproject_d.dll and in release this builds c:outputReleasemycppproject.dll.

One C# console application (mycsharpconsole.csproj) containing PInvoke calls into the DLL.

All compiles fine.

When I build, I would like to be able to add a reference from the csharp project to the cpp DLL project so that it can copy the appropriate file from the appropriate directory into the inDebug directory the csharp project is built into.

This should be possible, since the IDE knows everything there is to know about where the DLL gets built, and where the C# application gets built.

In Visual Studio 2010:

I've tried "Dependencies..." on the csharp project and adding a dependency on mycppproject, but that has no effect.

I've tried "Add Reference..." on the csharp project and adding a reference to the cpp project, but I get a warning message 'The Target Framework version for the project "mycppproject" is higher than the current project Target Framework version. Would you like to add this reference to your project anyway?' (Yes/No/Cancel).

Clicking "Yes" produces the error message "A reference to mycppproject" could not be added."

question from:https://stackoverflow.com/questions/5107694/how-do-i-add-a-reference-to-an-unmanaged-c-project-called-by-a-c-sharp-project

Answer 1

Visual Studio doesn't support referencing an unmanaged C++ project from a managed C# one, but MSBuild supports referencing any project from any other project.

You can manually add a reference to your project by editing the .csproj file by hand. In the file, find your existing set of ProjectReference elements (or add a new ItemGroup if you don't have one) and add the following reference:

<ProjectReference Include="..mycpproject.csproj">
  <Project>{b402782f-de0a-41fa-b364-60612a786fb2}</Project>
  <Name>mycppproject</Name>
  <ReferenceOutputAssembly>false</ReferenceOutputAssembly>
  <OutputItemType>Content</OutputItemType>
  <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
</ProjectReference>

When you perform the build, the reference will cause MSBuild to build the referenced project first. The ReferenceOutputAssembly value tells MSBuild not to copy the output assembly of the build (since the C++ project does not produce one), but the OutputItemType and CopyToOutputDirectory values instruct it to copy the output content to the referencing project's output folder.

You will be able to see the reference in Visual Studio, but you can't do much with it there.

This answer is based on a similar problem solved by Kirill Osenkov on his MSDN blog: https://blogs.msdn.microsoft.com/kirillosenkov/2015/04/04/how-to-have-a-project-reference-without-referencing-the-actual-binary/