VBA and C# interop

Mark Morrisson

Hi everyone,

I need to call a DLL in C# from a VBA application. The DLL will expose a method that returns a complex class. I tested the interop and it worked fine when the method returns a primitive type, but when it returns a complex object, it does not work.

I precise I don't know anything at COM (I don't even understand how those GUIDs are generated!), I have Visual Studio .NET Express, what's the easiest method you would recommend to me?

Thanks in advance,
Mark

4 Replies

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Vulpes14y ago
Accepted answer
Unfortunately COM is anything but simple but I've found something here which might help :

http://blogs.artinsoft.net/Mrojas/archive/2010/06/23/Exposing-C-Classes-thru-Interop.aspx
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Mark Morrisson14y ago
Thank you very much!
Mark
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Mark Morrisson14y ago
In fact, Visual Studio does all this stuff for you if you check the right options (registering the COM object and making them visible). As I said in my question, the problem is not to build a DLL that exposes a method, it's to build a DLL that exposes a method that returns a complex type. It does not work alone, so I'm looking for a simple tutorial/explanation to learn how to do it the simple way.
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Vulpes14y ago
The only realistic way for C# to interoperate with VBA is using COM, so I imagine you must have already created a COM-aware DLL and registered it with tlbexp.exe for anything to work at all.

As far as exposing your own classes are concerned they must be public and, to be on the safe side, they should be decorated with the attribute [ComVisible(true)].

So I'd try that if you're not doing it already.
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