how to use a ContextBoundObject to intercept a function call before/after the invocation?

I have read this article and I can't find a good example for how to use a ContextBou开发者_如何学编程ndObject to intercept a function call.

Can anyone show me how it's done?

Also, a side question: Why can't I use a ContextBoundObject with a generic class? I am asking accroding to this msdn reference