registration free COM without copying the dll to the same directory as the executable

Question

How can I consume a registration free COM object without copying the dll to the same directory as the executable? Is this possible?

I would like a complete working sample or a detailed step-by-step guide for my exact scenario.

For example, I have the following components:
CppTestRunner.exe - vc++ console application
CppTests.dll - vc++ mfc dll
CsCOMServer.dll - c# COM visible dll

I do not want to modify the exe or its directory, like adding an external manifest.
CppTests.dll is in a different directory than the exe.
It is okay if CsCOMServer.dll is in the same directory as CppTests.dll.

CppTestRunner.exe calls LoadLibrary on CppTests.dll which works fine.

After embedding manifests and using the windows activation context apis, I was able to copy CsCOMServer.dll to the exe directory to verify that CppTests.dll can create an instance of CsCOMServer.dll without issues, but again, I am trying to avoid this step.

Currently, with CsCOMServer.dll in the same directory as CppTests.dll, and without CsCOMServer.dll in the exe directory, I am getting the following error when I call CoCreateInstance:
Error = 0x80070002 The system cannot find the file specified.

I have used sysinternals process monitor to track down the paths CppTestRunner.exe looks in, etc.
I notice that depending on the things I try to do, sometimes CppTestRunner.exe tries to read CsCOMServer.dll.config in the same directory as CppTests.dll, but no matter what I try to put in there, I was not able to get past the error.
Also depending on other things I try to do, CppTestRunner.exe tries to read CsCOMServer.dll in the same directory as CppTests.dll but for some reason, I still get the same error.

Anyone know of working code with this exact scenario?

As you can probably tell, this is part of some unit\integration tests.

As a simple workaround, I am currently copying CppTestRunner.exe to the same directory as CppTests.dll and running it from there, but would like to avoid this step.

Thank you.

Answer 1

.NET looks for managed registration-free COM first in the GAC, then in the executable's folder. It uses the activation context to read activation metadata, but not to determine the location of the files themselves.

Answer 2

You can save the DLL in a sub Folder, let say DLLFolder\YourDll.dll, and in the manifest file of yourDll, write the filename like

<file name = "DLLFolder\YourDll.dll">

But you need to keep the manifest file (of the DLL) in the location where the EXE is saved.