Manual Painting Issue

Answer 1

Add following in New (after InitializeComponents):

this.SetStyle(ControlStyles.ResizeRedraw, true);

This is to ensure painting on resize.

There are few additional styles that you may try (AllPaintingInWmPaint, UserPaint...) but whether they should be set or not depends on your particular case and what exactly you want to do. In case that all painting is done by you in Paint event, I would set them.

Answer 2

I would suggest creating your own panel, derive it from panel and place the following in the constructor:

  this.SetStyle(ControlStyles.AllPaintingInWmPaint 
              | ControlStyles.OptimizedDoubleBuffer
              | ControlStyles.ResizeRedraw 
              | ControlStyles.DoubleBuffer 
              | ControlStyles.UserPaint
              , true);