title: How to get attribute value from node using xpath?
body: <p>Totally new to xpath.</p>
  
  <p>I have xml:</p>
  
  <pre><code>&lt;Values&gt;
     &lt;Value Value="a" CustomAtr="1" /&gt;
     &lt;Value Value="b" CustomAtr="2" /&gt;
     &lt;Value Value="c" CustomAtr="3" /&gt;
  &lt;/Values&gt;
  </code></pre>
  
  <p>To get value by index, i can use: <code>string(/*/Value[1]/@CustomAtr)</code></p>
  
  <p>Is it possible to get value by key?
  Hot to get <code>CustomAtr</code> value where <code>Value="b"</code> ?</p>
  
  <p>Thank you</p>