using System.Drawing.DLL in standalone

In my project I use System.Drawing.DLL, I have put the dll in my asset folder. It works fine in the editor However when I create a standalone one of my gameobjects that I have linked to my script through the GUI appears null ( only in the standalone, not in the editor). I have narrowed down the problem to come from the line using the drawing DLL :

 public List <PointF> lookingPoints;

if I comment this line, my otherGameObject become non null. I think the standalone is able to access the DLL because i have put it in my root folder of my unity project ( near the executable file) and the output_log gives me :

Platform assembly: C:\Users\flarradet\Documents\phd\keyboard\keyboard_browser\keyboad_Data\Managed\System.Drawing.dll (this message is harmless) Loading C:\Users\flarradet\Documents\phd\keyboard\keyboard_browser\keyboad_Data\Managed\System.Drawing.dll into Unity Child Domain

So What is the problem? Thank you