refresh window when working with graphics

Hi there
i created the appropriate classes that draw some polygons and lines on panel.

my problem is:

1. when i resize or move my window the shapes dissapears. i need to redraw the window - i notice the function onpaint and the e argument. what is that argument and how i use this function considering my 4 classes.?

thanks allot

u'll have to put all drawing code logic in the OnPaint