title: where can i find "ActiveDirectory" reference to add in my project?
body: <p>i have an issue using </p>
  
  <pre><code>System.DirectoryServices.ActiveDirectory
  </code></pre>
  
  <p>namespace in my project. visual studio gives me an error the :</p>
  
  <pre><code>The type or namespace name 'ActiveDirectory' does not exist in the namespace 'System.DirectoryServices'
  </code></pre>
  
  <p>i need to add reference to solve this problem.
  thanks for any help</p>