title: Xpath query to find elements which contain a certain descendant
body: <p>I'm using Html Agility Pack to run xpath queries on a web page.  I want to find the rows in a table which contain a certain interesting element.  In the example below, I want to fetch the second row.</p>
  
  <pre><code>&lt;table name="important"&gt;
  &lt;tr&gt;
    &lt;td&gt;Stuff I'm NOT interested in&lt;/td&gt;
  &lt;/tr&gt;
  &lt;tr&gt;
    &lt;td&gt;Stuff I'm interested in&lt;/td&gt;
    &lt;td&gt;&lt;interestingtag/&gt;&lt;/td&gt;
    &lt;td&gt;More stuff I'm interested in&lt;/td&gt;
  &lt;/tr&gt;
  &lt;tr&gt;
    &lt;td&gt;Stuff I'm NOT interested in&lt;/td&gt;
  &lt;/tr&gt;
  &lt;tr&gt;
    &lt;td&gt;Stuff I'm NOT interested in&lt;/td&gt;
  &lt;/tr&gt;
  &lt;/table&gt;
  </code></pre>
  
  <p>I'm looking to do something like this:</p>
  
  <pre><code>//table[@name='important']/tr[has a descendant named interestingtag]
  </code></pre>
  
  <p>Except with valid xpath syntax.  ;-)</p>
  
  <p>I suppose I could just find the interesting element itself and then work my way up the parent chain from the node that's returned, but it seemed like there ought to be a way to do this in one step and I'm just being dense.</p>