Mixing net standard and visual c++

Flade, David 20

Hello

Using VS 2017, can one have both net standard 2.0 and visual c++ projects in the same solution with the net standard project referencing the visual c++ project (.vsxproj)?

If I create one solution containing two projects of this kind using VS 2017 (both projects are empty) and the net standard 2.0 project adds the visual c++ project using "Add->Reference->Projects-><file path to .vsxproj>" then compilation doesn't work with the following error:

"C:\Program Files\dotnet\sdk\2.1.526\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.Sdk.targets(129,5): error NETSDK1007: Cannot find project info for 'C:\Users<Me>\source\repos\ClassLibrary1\Project1\Project1.vcxproj'. This can indicate a missing project reference."

Thanks

Regards

Flade, David 20 Reputation points

2024-05-21T08:58:25.9066667+00:00
I can successfully compile via Command Line when I do this:

dotnet restore (Note: If I don't do this, then step 2 doesn't compile with the same error as when I compile from within the VS 2017, see initial coment. If I right-click on the solution inside the VS 2017 and do a "Restore Nuget packages" then there is also the same compilation error as in the initial comment).

"C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\MSBuild\15.0\Bin\MSBuild.exe" ClassLibrary1.sln /t:Rebuild /p:Configuration=Release /p:Platform=x64 /p:VisualStudioVersion=15.0
Flade, David 20 Reputation points

2024-05-21T08:59:14.6966667+00:00

I would like to be able to compile from within the VS 2017. What should I do?
Hui Liu-MSFT 44,631 Reputation points Microsoft Vendor

2024-05-21T14:30:29.17+00:00

Hi,@Flade, David. Welcome to Microsoft Q&A. To have both a .NET Standard 2.0 project and a Visual C++ project in the same solution in Visual Studio 2017, with the .NET Standard project referencing the Visual C++ project, you need to ensure compatibility and proper project configuration. However, directly referencing a Visual C++ project from a .NET Standard project is not a typical scenario and is likely causing the issues you are seeing.

Steps to Integrate and Compile Successfully:

Ensure Compatibility:

Make sure both projects target compatible platforms. The .NET Standard project should be able to interact with the output of the Visual C++ project.

Interop via P/Invoke or C++/CLI:

Instead of directly referencing the Visual C++ project, you should consider using Platform Invocation Services (P/Invoke) or a C++/CLI wrapper. This allows the .NET Standard project to call functions from the C++ library.

Using P/Invoke:

P/Invoke allows managed code to call unmanaged functions implemented in DLLs.
Using C++/CLI Wrapper:

You could refer to here to install C++/CLI support.
Flade, David 20 Reputation points

2024-05-21T14:45:28.48+00:00

Thanks a lot for your quick support!

Just some comments related to your response.

The Visual C++ project targets
<TargetFrameworkVersion>v4.7.2</TargetFrameworkVersion>
which should be compatible with NET Standard 2.0.

Note: in my real scenario there is a native C++ project which is used by the Visual C++ Managed project which itself is used by the NET Standard 2.0 C# project. When compiling the code using Command Line (using call from above) it all works fine, and I can also run the program (there is a Command Line Tool around it). The the functionality implemented in C++ can correctly be used from within C#. So the compatibility should be there. It must be VS 2017.

Note as well: When I do the whole thing using Visual Studio 2022 all compiles inside the VS as well. Only with VS 2017 it doesn't work (only using the Command Line).
Hui Liu-MSFT 44,631 Reputation points Microsoft Vendor

2024-05-22T13:32:24.59+00:00
Hi,@Flade, David. I tested these steps in Visual Studio 2017 and Visual Studio 2022 and did not reproduce your issue.
1.Create CLR Class Library (.NET Framework) Application [name:ClassLibrary2]

2.Create Class Library (.NET Standard) [name:ClassLibrary1]-> Right click on Class Library (.NET Standard) project to add reference -> Check CLR Class Library (.NET Framework) Application project to add reference.

using System;using System.Runtime.InteropServices; using ClassLibrary2; namespace ClassLibrary1 { public class Class1 { } }

ClassLibrary1.csproj:

<Project Sdk="Microsoft.NET.Sdk"> <PropertyGroup> <TargetFramework>netstandard2.0</TargetFramework> <Platforms>AnyCPU;x64</Platforms> </PropertyGroup> <ItemGroup> <ProjectReference Include="..\ClassLibrary2\ClassLibrary2.vcxproj" /> </ItemGroup> <ItemGroup> <Reference Include="ClassLibrary2"> <HintPath>..\x64\Debug\ClassLibrary2.dll</HintPath> </Reference> </ItemGroup> </Project>

Could you share the steps to reproduce the issue?
Flade, David 20 Reputation points

2024-05-23T14:16:31.59+00:00

Added answer here by mistake. Please see my comment from May 23, 2024, 4:24 PM!
Flade, David 20 Reputation points

2024-05-23T14:24:37.46+00:00
Hi @Hui Liu-MSFT , I agree, your example works. However, this is not the case I was asking for. You were referencing a .NET Framework class library inside a .NET Standard class library. This works fine.

I want to reference a Visual C++ class library from within a .NET Standard class library. When doing this I get the error from above. Referencing a Visual C++ class library from within a .NET Framework class library works without any problems.

This is the csproj file from the .NET Standard class library:

<Project Sdk="Microsoft.NET.Sdk"> <PropertyGroup> <TargetFramework>netstandard2.0</TargetFramework> </PropertyGroup> <ItemGroup> <ProjectReference Include="..\ClassLibrary2\ClassLibrary2.vcxproj" /> </ItemGroup> </Project>

Many thanks for your support and help,

David

Accepted answer

RLWA32 41,456 Reputation points

2024-05-24T11:43:57.33+00:00

Now, in the same solution I want to create a third library which is a native C++ library using Visual C++ -> Empty Project (in the way I described it in my previous post) [name:UnmanagedLib]. UnmanagedLib shall be referenced from inside ClassLibrary2 (the C++/CLI one).

The Empty project template defaults to creating a C++ console application.

Clarify whether you intend to build a native C++ static library or intend to build a native C++ DLL and its related import library (.lib file).

Update:

In my own test I found that eliminating the project reference from the C++/CLI project to either the project that creates a static library or a dll and instead setting the linker property page to add the appropriate path to "Additional Library Directories" and the .lib file names to "Additional Dependencies" solved the problem. The solution then built successfully within VS2017.
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Hui Liu-MSFT 44,631 Reputation points Microsoft Vendor

2024-05-24T07:53:54.3366667+00:00

Hi,@Flade, David.

. NET project reference does not support native C++.

The operation of referencing C++ projects is problematic in itself. Even in Visual Studio 2022, it is not feasible.

Building in Visual Studio 2022 is fine, but it will not reference C++ projects. There is a warning icon exclamation mark on the project.

You could use C++ from C# via P/Invoke or C++/CLI.

If the answer is the right solution, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".

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Flade, David 20 Reputation points

2024-05-24T09:01:30.1133333+00:00

@Hui Liu-MSFT, many thanks for your answer. You are totally. I chose the wrong project type.

In fact, I want to to use a function implemented in native C++ code from within a NET Standard library in C#. I want to use C++/CLI as a bridge between the C# and the native C++ code. Eventually, I want to use the NET Standard library in both NET Framework and NET 6/8 application environments. In my previous comment I chose the wrong project type.

Now -using the correct project types as you pointed out - I created it this way:

a NET Standard 2.0 project that references [name:ClassLibrary1]

a NET Framework 4.7.2 C++/CLI project (in VS 17 created via Visual C++ -> CLR -> CLR Class Library [name:ClassLibrary2]

This compiles successfully.

Now, in the same solution I want to create a third library which is a native C++ library using Visual C++ -> Empty Project (in the way I described it in my previous post) [name:UnmanagedLib]. UnmanagedLib shall be referenced from inside ClassLibrary2 (the C++/CLI one). When compiling this, I get again the error as in my inital question:

Cannot find project info for 'C:\Users\Me\source\repos\ClassLibrary2\UnmanagedLib\UnmanagedLib.vcxproj'. This can indicate a missing project reference.

On the console I can compile this successfully using the steps I described in my initial post.*
*
If I do exactly the same thing but using a NET Framework class library instead of a NET Standard class library as ClassLibrary1 then all compiles successfully from within VS 2017.

Is there a way that I compile the solution in the setup described above from within VS 2017?

Flade, David 20 Reputation points

2024-05-24T14:32:06.9833333+00:00

Hello @RLWA32 ,

Thanks, like this it indeed compiles using VS 2017! Thanks for this great support!

Interestingly, that this only needs to be done this way when the C# library is NET Standard. You can use the project reference kind-of-way when the C# library is NET Framework.

Anyways, I will accept this answer! Great work! Thanks.

David

RLWA32 41,456 Reputation points

2024-05-24T14:43:48.5233333+00:00

@Flade, David, You're welcome! I'm glad that my suggestion to adjust the linker properties for the C++/CLI project solved the problem.

I converted the comment to an Answer that can be accepted.

Flade, David 20 Reputation points

2024-05-24T14:49:26.4533333+00:00

@RLWA32 Thanks. I accepted your answer there!
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Mixing net standard and visual c++

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