title: How can I update a specific XElement?
body: <p>What is the best way to update an XElement (<strong>update the value of itemNumber of element Pen</strong>) in this XML? </p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;MyStore&gt;
    &lt;Category&gt;
      &lt;itemName&gt;Pen&lt;/itemName&gt;
      &lt;itemNumber&gt;12&lt;/itemNumber&gt;
    &lt;/Category&gt;
    &lt;Category&gt;
      &lt;itemName&gt;Paper&lt;/itemName&gt;
      &lt;itemNumber&gt;23&lt;/itemNumber&gt;
    &lt;/Category&gt;
  &lt;/MyStore&gt;
  </code></pre>