title: How to redraw specific rectangle of control in C#?
body: <p>From the logic of my program I know I need to redraw the rectangle between <code>top_left = {x=32,y=32}</code> and <code>bottom_right = {x=64,y=64}</code> of a simple WinForms <code>Control</code>. I don't want to redraw <strike>the whole client area</strike> but only a part of it (performance reasons). WinApi can't tell what part must be redrawn, I must tell it. So how can I do that ?</p>
  
  <p>The rectangle to redraw is different every time I need this feature.</p>
  
  <p>I thought:</p>
  
  <ul>
  <li>send <code>WM_PAINT</code> message (but I can't figure out how to transmit the rectangle, since wParam and lParam are always 0 when this message usually arrives)</li>
  <li>...</li>
  </ul>
  
  <p><em>(Hope this is not duplicate. I'll remove if it is.)</em></p>