Choosing the Right COM Component Type

Here is a list of the major types of COM components and the things that they do best:

• In-process components (ActiveX DLLS): Best for performance.

• Out-of-process components (ActiveX EXEs): Best for background, asynchronous processing. Best for exposing an application's object model to clients.

• ActiveX controls: Best for objects that have mainly to do with standardizing parts of the user interface.

• Active documents: Best for objects that need to run across the Internet or an intranet.

Some less-than-positive considerations for various COM component types:

• In-process components (ActiveX DLLS): Problems if you give them a user interface. Crashes clients more readily than EXEs.

• Out-of-process components (ActiveX EXEs): Slower than DLLs or controls.

• ActiveX controls: Perform worse than DLLs, but better than EXEs.

• Active documents: Performance not good. Not particularly helpful in exposing an object model.