title: XmlDocument.SelectNodes question
body: <p>What's the difference using root node to select and using document object to select nodes?
  Which way is preferred.</p>
  
  <p>For example,</p>
  
  <p>1.</p>
  
  <pre><code>XmlDocument Doc = new XmlDocument();
  Doc.Load(mem);
  
  XmlNodeList nodeList = Doc.SelectNodes(@"//@id");
  </code></pre>
  
  <p>2.</p>
  
  <pre><code>XmlDocument Doc = new XmlDocument();
  Doc.Load(mem);
  
  XmlElement root = Doc.DocumentElement;
  
  XmlNodeList nodeList = root.SelectNodes(@"//@id");
  </code></pre>