title: How can I override HtmlTextWriter for ASP.NET AJAX UpdatePanel requests?
body: <p>I have inherited System.Web.UI.HtmlTextWriter to do some custom rendering of HTML in an ASP.NET application.  This is configured in my Web.config file using the following:</p>
  
  <pre><code>&lt;browserCaps&gt;
    tagwriter="MyAssembly.CustomHtmlTextWriter, MyAssembly"
  &lt;/browserCaps&gt;
  </code></pre>
  
  <p>This works correctly for regular page requests, the overridden methods such as OnTagRender are called and the customised HTML is sent to the browser.</p>
  
  <p>However, when doing an asynchronous postback using an UpdatePanel this code is never called and the HTML arrives in the browser without my custom modifications.  Am I missing some configuration that will load my custom HtmlTextWriter for AJAX requests?</p>