title: get specific attribute from html input
body: <p>I can get value from html input by:
  Request["inputID"]</p>
  
  <p>But, How to get <strong>data-myatt</strong> attribute from input below in server-side:</p>
  
  <pre><code>&lt;input id="input1" type="text" value="value" data-myatt="my date" /&gt;
  </code></pre>