title: How to clean up after myself when drawing directly to the screen
body: <p>I'm drawing directly to the screen using <code>BitBlt</code> and <code>GetDC(IntPtr.Zero)</code>.  Is there some way to call Refresh or Invalidate on the whole screen when I'm done, so that I don't leave big chunks of paint everywhere (digitally speaking)?</p>
  
  <p><strong>Update:</strong>  when you draw directly to the screen like I'm doing, whatever you draw remains there until the window underneath it repaints itself (and in so doing, repaints the portion of the screen it's covering).</p>
  
  <p>The problem is that some portions of the windows desktop don't repaint themselves for long periods.  For example, if I draw over top of the task bar, the actual tasks repaint themselves fairly quickly (along with the Start button etc.), but the taskbar itself retains what I've drawn for as long as a couple of minutes.</p>
  
  <p>If my app had a window that covered the entire screen, I would just call <code>Invalidate()</code> on that form which would cause it to repaint itself and thus the entire screen.  What I need is some way of calling <code>Invalidate</code> or <code>Refresh</code> on the whole screen itself.</p>