title: SelectSingleNode method on XmlNode returns undefined value
body: <p>I have a simple xml, I created a XmlDocument out of it and used Xpath to fetch a node, I need to pass this node to other parts of the code where I may use further xpath functions on the XmlNode object to get other sub nodes. But in the code below</p>
  
  <pre><code>string xmlString = "&lt;catalog&gt;&lt;music&gt;&lt;cds&gt;&lt;cd&gt;&lt;title&gt;First Title&lt;/title&gt;&lt;author&gt;Author    1&lt;/author&gt;&lt;/cd&gt;&lt;cd&gt;&lt;title&gt;Second Title&lt;/title&gt;&lt;author&gt;Author 2&lt;/author&gt;&lt;/cd&gt;&lt;/cds&gt;&lt;/music&gt;&lt;/catalog&gt;";
  XmlDocument xmlDocument = new XmlDocument();
  xmlDocument.LoadXml(xmlString);
  XmlNode musicNode = xmlDocument.SelectSingleNode("/catalog/music");
  XmlNode cdsNode = musicNode.SelectSingleNode("/cds");
  </code></pre>
  
  <p>when I print the name of the musicNode, I am getting "music", so I assume that I have the  "music" node. So I again applied xpath expression "/cds" on the music node assuming I would get the "cds" XmlNode, but cdsNode in the code returns undefined value, but if I do</p>
  
  <pre><code>XmlNode cdsNode = musicNode.SelectSingleNode("/catalog/music");
  </code></pre>
  
  <p>I am getting a valid value for cdsNode that is the "music" node again, I suppose musicNode represents the XmlDocument instead of the "music" XmlNode??? Am I missing something, I am from Java and in Java navigating to subnodes from Node is possible using xpath, like an xpath expression "/cds" on the musicNode would have returned a valid cdNode</p>