title: How do I convert a Dictionary to a Lookup?
body: <p>I have a Dictionary that has a signature: <code>Dictionary&lt;int, List&lt;string&gt;&gt;</code>. I'd like to convert it to a Lookup with a signature: <code>Lookup&lt;int, string&gt;</code>. </p>
  
  <p>I tried:</p>
  
  <pre><code>Lookup&lt;int, string&gt; loginGroups = mapADToRole.ToLookup(ad =&gt; ad.Value, ad =&gt; ad.Key);
  </code></pre>
  
  <p>But that is not working so well.</p>