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accessing external .net DLL from own .net 4.6.1 c# interop DLL

I need to modify my existing DLL in c# to interface between PowerBuilder 2017 (PB) and an external DLL developed by vendor. external.DLL is using .net 4.6.1
PB Target <-> my.DLL <-> external.DLL
I have set my.DLL up to be COM Interop enabled (Make assembly COM-Visible + Register for COM interop) and have previously set this to work in PB IDE without 'external.DLL' just fine by applying following commands:
regasm my.DLL
gacutil my.DLL (this is used only so PowerBuilder can access the DLL from within it's IDE)
Now, I try and reference external.DLL through my.DLL from PowerBuilder IDE I receive an error -3 code (Object could not be created).
How am I best to setup and also distribute both DLL files?
I think my issue is in setting up the References within Visual Studio 2017.
The COM interop is needed between PB and my.DLL.
I tried to add a follow Debug option as this would be helpful, but cannot trigger it.

Thank you for help.
I managed to get my.DLL working inside PowerBuilder IDE by using regasm on the external.dll and adding it also into the GAC.
For deployment of the PowerBuilder Application I expect to apply regasm to both DLL's and place them in same distribution folder.

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I have a C# .NET DLL that is exposed through COM Interop for which I have generated a manifest file. The DLL is being consumed through an Excel VBAProject using CreateActCtx and CreateObject to create my objects.
Everything works fine, however... I need to call regasm MyProject.dll /codebase or register with GAC. Otherwise I get ActiveX component can't create object or error in dll errors.
Is it possible to use a .NET DLL without having to register the DLL at all? I was able to do this previously with a VB6-based DLL and a manifest file.

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I have a dll created in VC++ and visual studio 2005 now i want to add same dll in my C# application and VS2010.
But whenever i tried it gives me erro
"a reference to "../name.dll"could not be added please make sure that the file is accessible and that it is a valid assembly or com component"

Seems like C++ dll is native dll (and not managed C++/CLI)
You need to look at P/Invoke.
Platform Invoke Tutorial
DLL Import

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You just register the dll with regsvr32.
Then add a reference, go to the COM tab, and choose your COM dll.

statically linking multiple VC++ libraries to a C++/CLI dll

So I have this C# project that requires the use of some functions from a vc++ library. This vc++ library is then dependent on other vc++ libraries.
So in order to get this working, I created a c++/cli dll project that wrapped the main vc++ library. In the project linker settings, I just added the target vc++ library in the input field, and this resolved linker errors. I then added a reference to the cli project to the c# project references.
Everything compiled fine, but when I ran the C# project, there was a File.IO.Exception saying that the cli dll couldn't be loaded. After some tinkering around, I found that this error was happening because the wrapped vc++ dll dependencies could not be loaded. So I copied the vc++ dll into the same folder as the c# exe. I also had to copy all of the other vc++ dlls that the initial dll depended on.
Having to keep track of all of the VC++ dlls is burdensome, so I'm wondering if it is possible to statically link all of the VC++ dlls into the C++/CLI dll, so I do not have to copy them into the same folder as the C# exe. I tried adding all of the vc++ dependencies to the linker input field but that didn't do anything.
Thanks,
Alex