COM Interop Error on 64 bit OS

13 Nov 2006 5:56 PM

ANeelima

I have a VB6 executable that references a .NET 2.0 dll.
The .NET 2.0 dll project has 'Register for COM Interop' checked. Thus,
compiling the dll will generate the .tlb file. This will allow early binding
to work from VB6.

I copied the VB6 exe and the .NET dll to a 32 bit OS. I copied the tlb file
to system32. When I execute the VB6 exe and call the .NET dll it works fine.

NOW, if I copy the VB6 exe and the .NET dll to a 64 bit OS and execute it, I
get the 'ActiveX cannot create object' error. I tried both, early and late
binding but I keep getting the same error.

If I call the .NET dll from another .NET app on a 64 OS, it works fine.

Is there anything different that I would have to do in order to get the VB6
application to call a .NET dll while running on a 64 bit OS?

--
ANeelima

14 Nov 2006 2:47 AM

Kevin Yu [MSFT]

Hi ANeelima,

After exporting a type library for .NET assembly, you will need to register
it in the registry. Regasm.exe does both for us. Are you copying the .dll
to a 64bit OS and register it with regasm.exe? If so, on a 32bit system all
works fine. However, on a 64bit system, regasm export and register the
assemly as 64 bit and write to the keys in 64 bit registry. The VB6 .exe is
a 32bit app, and running on WOW64, it cannot see the 64bit registry. That's
why the error is generated.

On a 64bit system, you have to do more steps:

1. Export a type library using tlbexp.exe with /win32 to force to generates
a 32-bit type library.
http://msdn2.microsoft.com/en-us/library/hfzzah2c(VS.80).aspx

2. Use regtlb.exe to register the type library.

The RegTlb tool requires a pre-existing TLB, but it is not a standard tool
included in any SDK, tool or system I know of, but just a sample program:

http://msdn.microsoft.com/library/en-us/dncomg/html/dcomtyplib.asp

You can download the pre-built RegTlb from the following link:

http://www.freevbcode.com/ShowCode.Asp?ID=2195

Please also check the following link for more info.

http://groups.google.com/group/microsoft.public.dotnet.framework.interop/bro
wse_thread/thread/9bfaa79d9bcf48d9/83f34e9241058ac0?lnk=st&q=regtlb&rnum=1#8
3f34e9241058ac0

If anything is unclear, please feel free to let me know.

Kevin Yu
Microsoft Online Community Support

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