WIX: COM registration fails when installing COM dll into another folder

Question

I am using heat to harvest the COM dll and tlb files (let's call them MyLib.*, developed in VB.NET) to do the COM registration. Everything was working fine, when I install MyLib.dll and MyLib.tlb into my application's installation folder, i.e., INSTALLDIR. However, since we want to allow different versions of our SW to be installed on the same machine, and if they are using the same version of COM component, only one copy of the dll (I think each version of our SW should have its own tlb, please correct me if I am wrong) should be installed, we now want to install MyLib.dll into another folder, specifically PROGRAM_FILES\Common Files\SHARED_FOLDER_NAME, so now if one version of our SW is uninstalled, the MyLib.dll will not be removed and can still be used by other versions.

But here comes the problem: my COM registration is just simply not working any more after I install this dll into this another folder, and it keeps saying that can't find file specified when I am calling the COM function which indicates registration failure. In the WIX installer project, everything is the same except this folder for MyLib.dll.

Here is the registry structure after installation:

Firstly I have HKCR\CLSID{MYCLSIDs}, each of them represents one of my COM class. in the sub-key named "InprocServer32", I have Assembly, Class, CodeBase, RuntimeVersion, threadingModel. And the CodeBase is either common file folder (not working) or MyApp's installation folder(working), which is the different locations I put the dll. I thought there would be another sub-key TypeLib under {MYCLSIDs}, since Access only sees the TypeLib and I think there should be some link from the TypeLib to the actual dll, however, at both cases this sub-key is missing but in the second case it is still working. Is there a problem of it?

Secondly I have HKLM\Software\Classes\CLSID{MYCLSIDs}, these keys are of course the same structure as described above.

Thirdly, the HKCR{MYPROGIDs}, these are just ProgIDs of my classes

Fourthly, HKCR\Typelib{LibID}, which includes the information from tlb file, and this ID is from the Assembly GUID of COM component project.

Finally, the HKEY_CLASSES_ROOT\Interface{InterfaceID}, there is sub-keys named ProxyStubClsid32 with value {00020424-0000-0000-C000-000000000046}, and the one named TypeLib and the value is my LibID.

As I mentioned, the only difference is the CodeBase, which stores where MyLib.dll is located. In order to verify that, I did two tests: after I install MyLib.dll into the shared folder, the COM calling fails. But if I replace all the CodeBase values for SHARED_FOLDER\MyLib.dll to INSTALLDIR\MyLib.dll, and copy MyLib.dll into INSTALLDIR, it actually works. Vise versa, after I install MyLib.dll into INSTALLDIR(in which case COM is working), I change the CodeBase values from INSTALLDIR\MyLib.dll to SHARED_FOLDER\MyLib.dll, and make a copy to SHARED_FOLDER, this time it fails. So it seems that it is exactly the installation location's problem, which is the opposite to my understanding of COM. And I don't think there is a permission issue for the SHARED_FOLDER(I could be wrong) since it is in a folder that my installer creates.

Please help, thanks!

Answer 1

It turned out that MyLib.dll is using some other libraries, which are still installed in the MyApp installation folder. And so in that case that MyLib.dll is installed in the shared folder, it tries to find those libraries in the same libraries, which of course fails. When I install those libraries in the shared folder too, it is working.

BTW I found fulogvw.exe very helpful when tracking down the assembly loading problem. For example in my case in the failed log it says can't load file xxx.dll in SHARED_FOLDER, the xxx.dll is some library that MyLib.dll is using, and I had no idea that MyLib.dll needs it until I see the log.