title: Force Form To Redraw?
body: <p>In C# WinForms - I am drawing a line chart in real-time that is based on data received via serial port every 500 ms.</p>
  
  <p>The e.Graphics.DrawLine logic is within the form's OnPaint handler.</p>
  
  <p>Once I receive the data from the serial port, I need to call something that causes the form to redraw so that the OnPaint handler is invoked.  I have tried this.Refresh and this.Invalidate, and what happens is that I lose whatever had been drawn previously on the form.</p>
  
  <p>Is there another way to achieve this without losing what has been drawn on your form?</p>