Can't instantiate multiple VFP COM Dlls: 80004005 Unspecified error

Question

I've got two sample VFP9 OlePublic dlls that I'm calling from a .NET Core 2.1 project running full framework .NET 4.6.1. Everything is working fine locally but upon deployment to a Windows Server 2016 machine, I'm only able to instantiate an instance of a.dll or b.dll, not both. It seems the last one to be registered wins.

If I register a.dll then b.ll, I can instantiate an instance of b & vice versa.

Retrieving the COM class factory for component with CLSID {CF0998BA-54F1-40BD-BB92-4E938A77E1E5} failed due to the following error: 80004005 Unspecified error (Exception from HRESULT: 0x80004005 (E_FAIL)).

Define Class miked As Session OLEPUBLIC
    
FUNCTION HelloWorld as String
    RETURN "Hello World"
ENDFUNC 

FUNCTION Echo(thingToEcho as String) as String
    RETURN thingToEcho
ENDFUNC 

Enddefine 

public void TestMikeDll()
{
    new miked.miked();
}

I'm guessing I haven't configured/defined something correctly in my VPF9 projects? 🤔

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update

So it's not the last one registered, it's the first one to get instantiated. If I successfully instantiate a.dll then b.dll fails but if I recyle the app pool & try b.dll first it succeeds & a.dll fails.

Answer 1

Give the AppPool identity write (maybe modify too) access to the location of the VFP COM Dlls. Apparently, it needs to dynamically create another DLL: [original name]r1.dll that has a file desc of "Microsoft Visual FoxPro 9.0 SP2 Runtime Library" (the purple box).

1. Go to properties on folder where COM DLLs live
2. Security Tab
3. Edit
4. Add
5. in enter the object names to select: IIS AppPool\[your AppPool name]

reference: MSFT doc page on giving AppPool identity file permissions

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credit: this comment from Aloio Kraus lead me down the path:

the 5 of the error code is the Win32 error code which means access denied. I would run procmon and watch for registry/file accesses which fail. That should hint to the right direction what went wrong