title: What is a fastest way to do search through xml
body: <p>Suppose i have an XML file, that i use as local database, like this):</p>
  
  <pre><code>&lt;root&gt;
   &lt;address&gt;
    &lt;firstName&gt;&lt;/firstName&gt;
    &lt;lastName&gt;&lt;/lastName&gt;
    &lt;phone&gt;&lt;/phone&gt;
   &lt;/address&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p>I have a couple of questions:<br>
  1. <em>What will be a fastest way to find address(or addresses) in XML where firstName contains 'er' for example?</em><br>
  2. <em>Is it possible to do without whole loading of XML file in memory?</em></p>
  
  <p>P.S. I am not looking for XML file alternatives, ideally i need a search that not depend on count of addresses in XML file. But i am realist, and it seems to me that it not possible. </p>
  
  <p><strong>Update:</strong>
  I am using .net 4<br>
  Thanks for suggestions, but it's more scientific task than practical.. I probably looking for more fastest ways than linq and xmltextreader.</p>