title: Get OU list from active directory using c# with hierarchy
body: <p>I want to retrieve OU structure from active directory using c# into a treeview
  So far I found <a href="https://stackoverflow.com/questions/2903541/acquiring-ad-ou-list">Acquiring AD OU list</a> 
  I have tested, it worked fine,this is good to get a flat list of all OUs without any hierarchies.</p>
  
  <p>How could I get hierarchical list with the extent of above method ? I am using .net 2.0 and VS 2010</p>