How to implement Change Size Frame in C#?

Here is the image: http://itbrigada.ru/img/size.png Need to implement the same sizing frame in WinForms app? What is the best way?

Implement thin frame (Custom Control) with that frame drawn on it and place the sizable frame inside and serve Mouse Events for undeneath frame?

Spy++ says it's just one window.

Also, I c开发者_如何学Goan resize it during runtime, what i'm looking for here is "how to implement that kind of resize border".