title: hidden field value lost after postback
body: <p>I have two hidden controls:</p>
  
  <pre><code>&lt;asp:HiddenField runat="server" id="pageHeader" /&gt;
  &lt;asp:HiddenField runat="server" id="pageInformation" /&gt;
  </code></pre>
  
  <p>I am calling following function from master page:</p>
  
  <pre><code>show_tip(this, document.getElementById('ctl00_pageInformation').value, document.getElementById('ctl00_pageHeader').value);
  </code></pre>
  
  <p>and i am passing values in hidden field on .cs page in page load as follows:</p>
  
  <pre><code> string message = Request.Form["pageInformation"];
   if (string.IsNullOrEmpty(message))
   {
        ((HiddenField)Master.FindControl("pageHeader")).Value = pageHeading;
        ((HiddenField)Master.FindControl("pageInformation")).Value = pageInformation;
   }
  </code></pre>
  
  <p>This is working fine, but on page <strong>POSTBACK</strong>, hidden fields lose their value. How can I retain the values after postback?</p>