title: Order XmlNodeList based on an attribute
body: <p>I have an <em>XmlNodeList</em> that contains packets (item) from the root of the XML example below. I want to sort the XmlNodeList based on the <em>node's key attribute value</em>.
  The sorting has to be very efficient, every millisecond counts.</p>
  
  <p>Do you have any idea?</p>
  
  <pre><code>&lt;root&gt;
      &lt;item key="1000000020"&gt;
          Content 20
      &lt;/item&gt;
      &lt;item key="1000000001"&gt;
          Content 1
      &lt;/item&gt;
      ...
      &lt;item key="1043245231"&gt;
          Content n
      &lt;/item&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p>Edit: 
  I already have an XmlNodeList constructed from the items. I do not have access to the XmlDocument anymore, only the list of items.</p>