COM Class Factories

Question

hey,

i was looking for some COM, .NET interoperability topics, and i came across a few legacy COM examples using c++, to round it up, i understood that u define every interface and coclass inside and idl (interface definition file) so other com aware languages can understand type information, but the only com class not defined in an idl file is the one derived from IClassFactory, can some one please tell why since other .NET languages need also to obtain a class factory to instintiate other com classes, so how can they understand the type information ??

Answer 1

Class factories are rarely used directly. In fact, if you needed to create a class factory first to create any COM object, how would you create the class factory itself?

COM library takes care of creating objects. E.g., if COM server is a DLL, it is required to export DllGetClassObject function. When a client wants to create a COM object, it calls CoCreateInstance specifying a CLSID. Using CLSID, COM library finds the server and (if it's a DLL) loads it and calls its DllGetClassObject.

This is just a couple of words on the topic. COM is a very big topic; you might have to start at the very beginning if you want to have complete understanding...