How to use ContextBoundObject to intercept a function call before / after a call?

Question

I read this article and I cannot find a good example of how to use ContextBoundObject to intercept a function call.
Can someone show me how to do this?

In addition, the question arises: why can't I use ContextBoundObject with a common class? I ask accroding this msdn link

Answer 1

I found this article that explains everything.