CODEWITHSUNDEEP
c++windowsvisual-studiocomvb6
Aram Hăvărneanu
Aram Hăvărneanu

Reputation: 784

How to load COM DLL at runtime

I have a VB6 COM DLL. I want to use it from C++. I know how to register it, generate a tlb file from the DLL, and #import it in C++.

I'd like however, to load and use DLLs like this dynamically, at runtime, without knowing them in advance. Is this possible?

Thanks,

Upvotes: 1

Views: 4365

Answers (3)

Frank Bollack
Frank Bollack

Reputation: 25166

Take a look at these two MSDN articles about Registration-Free Activation of COM Components:

There also have been some similar question here on StackOverflow:

Upvotes: 1

Vagaus
Vagaus

Reputation: 4215

IMHO, You need at least some common interface (so you known what to call in the C++ side).

I'd do something like:

  1. Define a common interface (in its own DLL/TLB)

  2. Implement this interface in one or more COM servers

  3. Import this interface in the C++ side (let's call it client)

  4. Define a way to pass the progid of the COM server you want to work with (load dynamically) in the client.

Hope this helps

Upvotes: 2

MSalters
MSalters

Reputation: 179917

Yes, but you need to get the question clearer.

Sometimes, you do know the COM interface upfront, just not the implementation. In that case, you can create a dummy implementation of the interface and #import that. At runtime, you'd still register the real component, get an object from it (via CoCreateInstance probably) and store that in an appropriate smart pointer.

With VB6, it's a bit less direct. This adds a level of indirection. Read up on IDispatch. You need to get that known interface to describe an unknown interface. That way, the unknown interface can be obtained at runtime.

Upvotes: 4

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