How do I reduce flicker when resizing a transparent Panel whose parent has a gradient background?

Windows Forms FAQs

How do I reduce flicker when resizing a transparent Panel whose parent has a gradient background?

Make sure to set these flags for your panel, e.g., in its constructor. You will have to derive a class from Panel otherwise if you were initially using the Panel directly.

base.SetStyle( ControlStyles.DoubleBuffer |
  ControlStyles.DoubleBuffer |
  ControlStyles.UserPaint, true );

Contributed from George Shepherd's Windows Forms FAQ