Question

I’ve created a .Net assembly that exposes an event. I can consume without problems the event from VB6. Now I’ve deployed the assembly to a PowerBuilder developer and he says he cannot handle events from COM objects if they are not ActiveX.

Are different the ActiveX events from the normal COM events? Should I implement some additional interfaces so PowerBuilder can ‘see’ the events?

Thanks in advance.

Answer 1

Both events are implemented via connection points (IConnectionPoint and friends). ActiveX controls typically implement the connections points with certain additional constraints:

• the controls themselves are of “Apartment” threading model and the events are to be fired off the STA thread where control was created from
• the outgoing event interface is a dispinterface, nevertheless it might have methods and properties in its declaration, the control would call IDispatch::Invoke to deliver the actual events.
• the outgoing interface declaration is available on the type library, and this is how ActiveX control consumer finds out about existing events
• the control lists the main and event interfaces of a coclass on the type library, and there is also implementation of IProvideClassInfo2 to also provide this information.

It might so happen that PowerBuilder or another COM event consumer relies on one or more of the items mentioned above, and as such it will only work with some event sources, and would refuse to work with other.