title: Convert from IEnumerable to ISet
body: <pre><code>public override ISet&lt;string&gt; SetCellContents(string name)
  {          
      HashSet&lt;String&gt; list = graph.GetDependents(name);
      return list;
  }
  </code></pre>
  
  <p><code>Graph.getDependents(name)</code> returns an <code>IEnumerable</code> of a <code>HashSet&lt;String&gt;</code>. I get an error:</p>
  
  <blockquote>
    <p>"cannot convert from IEnumerable to ISet"</p>
  </blockquote>
  
  <p>I am not sure what to do?</p>