title: Find Elements by Attribute using XDocument
body: <p>This query seems to be valid, but I have 0 results.</p>
  
  <pre><code>IEnumerable&lt;XElement&gt; users =
              (from el in XMLDoc.Elements("Users")
               where (string)el.Attribute("GUID") == userGUID.ToString()
               select el);
  </code></pre>
  
  <p>My XML is as follows:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8" standalone="yes"?&gt;
  &lt;Users&gt;
    &lt;User GUID="68327fe2-d6f0-403b-a7b6-51860fbf0b2f"&gt;
      &lt;Key ID="F7000012ECEAD101"&gt;
        ...
      &lt;/Key&gt;
    &lt;/User&gt;
  
  &lt;/Users&gt;
  </code></pre>
  
  <p>Do you have any clues to shed some light onto this?</p>