title: drawing new lines in an already populated canvas
body: <p>So I got on my grid a canvas which as its background it get a drawing brush from resource dictionary.That not a problem it works perfect …</p>
  
  <p>But now I need to draw an open ended polygon on it , which gets its coordinates as an array of X and Y. let’s say intX[i]  and intY[i] arrays…. So point 1 is intX[0]  and intY[0] and so on ….</p>
  
  <p>And after that depending on some calculation I will get some more attributes and I need to add some horizontals and vertical lines ‘no more polygons’ .
  After that I need to write the result on it … so on point (x1,y1) I need to WRITE the result</p>
  
  <p>Ps : is this even possible …. Is canvas a good choice ‘ I chose canvas because the coordinates should be absolute and doesn’t change when window or object is resized’ the newly drawn lines should not delete the previous drawn line or the background’
  Sorry or my bad English and I hope u can guide me with something to start with…. </p>