Transparent Control fun

Question

I'm using the technique in the article http://www.c-sharpcorner.com/Code/2003/May/TransparentControls.asp to make a user control transparent. The transparency part works perfectly, just as I need. However, a problem arises when I redraw the user control. I'm trying to simulate a protractor as a user control, and I want the user to be able to change its size. When the size of the protractor becomes smaller, the entire control is not redrawn, so there are remnants of the old protractor image still on the control. When I clear the background by force, the transparent effect is ruined. I can RecreateHandle() when the size changes, but I don't think this is very effecient. Any help or ideas?