Substituting for COM interfaces

[Tum4ik]

During migration from Moq to NSubstitute I've come up with the problem of mocking COM interfaces. It worked with Moq, but now I get the exception:
Microsoft.CSharp.RuntimeBinder.RuntimeBinderException : Cannot perform runtime binding on a null reference

It is possible to face with that case in my repository (branch: plugins).

So, is there something I don't know? Or maybe it requires additional development.

Thanks for help in advance.

[dtchepak]

Hi @Tum4ik ,

I haven't had a chance to try this out yet, but one thing to try is using Configure which will prevent the substituted class from running any real code while it is being set up (you will need to add using NSubstitute.Extensions;):

 _wshShell.Configure().CreateShortcut(Arg.Any<string>()).Returns(shortcut);

If that doesn't work please let me know and I'll try to reproduce it locally.

[Tum4ik]

Hi @dtchepak ,

Thank you for your response. Unfortunately, your suggestion didn't change anything. The exception is still present.

[dtchepak]

@Tum4ik Thanks for trying it out.

This may take me a bit of time to work out sorry as I don't currently have access to a Windows machine.

Is there any more info you can provide about WshShell that may give us some clues?

We've had some previous issues with dynamic that might be related?

• Extension methods don't work for dynamic returns #144
• Does not work with members that use dynamic #75

[Tum4ik]

Oh... I have exactly this case.
So, I am able now to fix the problem via:

SubstituteExtensions.Returns((IWshShortcut) _wshShell.CreateShortcut(Arg.Any<string>()), shortcut);

Thank you, @dtchepak!

[dtchepak]

Thanks for the update @Tum4ik . I don't normally work with dynamic so if you find a neater way for NSubstitute to support this case please let us know or send through a PR. 🙇