title: Poor performance issue when drawing lines on WP7
body: <p>I'm developing an application which has a part that allows you to draw using your fingers.</p>
  
  <p>To do that I've followed this tutorial (here's also the app with the source code):
  <a href="http://sigurdsnorteland.wordpress.com/2010/10/20/fingerpaint-a-little-wp7-paint-app/" rel="nofollow">http://sigurdsnorteland.wordpress.com/2010/10/20/fingerpaint-a-little-wp7-paint-app/</a></p>
  
  <p>And this (almost the same):
  <a href="http://www.geekchamp.com/tips/drawing-in-wp7-2-drawing-shapes-with-finger" rel="nofollow">http://www.geekchamp.com/tips/drawing-in-wp7-2-drawing-shapes-with-finger</a></p>
  
  <p>The problem (for both) is that if I draw a lot of lines the application becomes very slow making impossible to draw normally. Does this happen because I create too many lines that are kept in memory? And how can I solve this? I've seen many applications on the market that don't suffer of this issue...</p>
  
  <p>Thanks in advance :).</p>