Unable to interface Com Object built in Delphi XE3

Question

We have an Delphi application that has a built in com object. When compiled in Delphi XE3 (Windows 8) we can't reference it from Visual Studio C#. However, an older version that was compiled in Delphi 2010 (Windows 7) works as expected.

The com object registers without errors and i can access it by using VBA script in Excel. Has anyone come accross something like this?

Answer 1

The most likely explanation is a bitness mismatch. I'm assuming that the COM server is 32 bit since you have been compiling it in Delphi 2010.

Suppose that your COM server is an in-proc server. Then I guess that your failing host is a 64 bit application. If so then you need to make the bitness match. Most probably by switching your host to be 32 bit by targeting x86.

If the COM server is out-of-proc then the issue is with registration rather than executable bitness matching. It will be registered in the 32 bit registry view, but your 64 bit host is looking in the 64 bit view. This would explain why your 32 bit Excel VBA code can find it. You need to register the server in both 32 and 64 bit registry views. Or switch the host to 32 bit.