title: NLog extensions add assembly programmatically
body: <p>I am using nlog v3 and I cannot figure out the way to do programatically what </p>
  
  <pre><code>  &lt;nlog&gt;
      &lt;extensions&gt;
        &lt;add assembly="NLog.MongoDB" /&gt;
      &lt;/extensions&gt;...
  </code></pre>
  
  <p>does. 
  I found one answer on old Nlog forums, that could've helped, but it was for v1 and v2 and these classes are no longer there.
  Anybody knows how to do it in code?</p>