title: Need Hashtable and Arraylist
body: <p>I am trying to use someone else's C# classes in my Windows 7 Phone app.  The classes use objects of type Hashtable. </p>
  
  <p>The file in question has</p>
  
  <pre><code>using System.Collections;
  </code></pre>
  
  <p>at the top, so I'm assuming that's the Hashtable object it wants.  </p>
  
  <p>When I try to build my solution, I get errors that the type or namespace name 'Hashtable' could not be found, are you missing a using directive or assembly reference.</p>
  
  <p>In Microsoft's documentation of Hashtable, I see it says Assembly: mscorlib</p>
  
  <p>But if I try to add mscorlib via Project>Add Reference, VS says it can't add it because it is automatically referenced by the build system.</p>
  
  <p>What am I missing?</p>