Resizable custom user control and redraw problem

I usually use standard GUI controls provided be .NET. Now I need to create something different. I need to create start window, that contains other custom controls. This window should be resizable (so should be all the inside controls) and I need to do smth to draw it smoothly.

I created MyResizableControl where I adjust all elements to the size, and my start window and custom controls inherit from it. But when the start window is drawn, it is drawn with background first, and then the controls are drawn on it. It can be seen by eye and looks ugly. It happens every time I minimize and maximize the window, and when I resize it. Can anybody give me some tips to improve it and/or some links to literature about it.