I am working on a resizer control and one of the problems I am facing is how to detect when a control is sited on the form? One way to do this is obviously to use a timer and continusly check the UserControl.Extender.Parent.Controls.Count value for changes, but I was thinking the might be a better more effective way e.g. by subclass the form and trap a message. I'm sure how to go about with that though, if it's even possible - anyone, hard core enough?

I am already using subclassing for other things so I'm not strange to the subject, I'm not considering me an expert though.