C4642 Warning in C++ CLR Library (DLL) with Winform (.Netcore8)

Question

I am getting this warning in my C++ CLR DLL with Winform in .NetCore 8

warning C4642: 'IHandle': could not import the constraints for generic parameter 'THandle'
warning C4642: 'HandleRef': could not import the constraints for generic parameter 'THandle'

The thing is, even with a very clean project, this warning exist just by default code.

Here are the steps

1. Create new project and selecting "CLR Class Library (.NET)"
2. Add a new form by going, Add-> New Item-> UI->Window Form
3. open the .vcxproj and removed references to

    System, 
    System.Data
    System.Drawing
    System.Windows.Forms
    System.Xml

and replaced with

  <FrameworkReference Include="Microsoft.WindowsDesktop.App.WindowsForms" />

Build and Clean and the Warning C4642 appears.

The thing is, this is just a unit test, Our actual project that we ported was originally a Winform C++ CLR app, now built as a DLL and has a C# host to make it work with .netcore 8.
It can be compiled and opened succesfuly.
BUT
We have so many of this warning as we have a LOT of forms is everywhere.

Any idea how to solve this, or should we just suppress this warning?

Answer 1

Hi, @cebuhax0r

As Viorel said, *where THandle : unmanaged'*generic constraint is available in new C#. C++CLR does not fully support new features.

You can disable the warning or use .NET 7.0 instead.

Best regards,

Minxin Yu

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