This help article offers a few performance tips with code examples on pages where you have used RadAjaxManager to
AJAX-enable many controls.
Using a RadAjaxManager control allows you to easily create settings that update many controls on the page.
Having a large number of AJAX-enabled controls to update, can both help with a performance problem by rendering smaller portions of the page
(which is why most developers use AJAX) and worsen the situation by triggering unnecessary DOM layout updates. Dealing with the DOM performance
problem will require actions specific for the current scenario.
Optimizing DOM Updates
Most of the slowdown happens when updating multiple controls in a table element. Every DOM update triggers a set of layout recalculations
that take up unneeded time. Consider the HTML in Example 1:
Example 1: A simple table with labels.
<div id="Header" style="width: 100%;" runat="server">
<table id="Table3" cellspacing="0" cellpadding="0" border="0" width="100%">
<asp:Label ID="lblStatus" runat="server" />
<td style="height: 25px">
<asp:Label ID="lblMessage" runat="server" />
Having two AjaxSettings for both labels will cause two DOM element updates: the spans rendered by
lblStatus and lblMessage, respectively. This will make the browser recalculate the table size twice.
You can optimize the process by updating the TABLE or the outer DIV element. Updating the Header control will update both labels and will trigger one
DOM update only.
Prohibitively bad performance is usually the result of updating controls that are placed deeply inside nested tables. In addition, most browsers
are slow when rendering elements with percentage dimensions (typically width or height of 100%), so another way to optimize this is to switch to
sizes in pixels. You could also use a fixed table layout by setting an HTML table's CSS style property table-layout to fixed:
Note that you will need to define width and <colgroup> and <col> elements for your table when using fixed table layout.
Other Performance Boosters
If your page has too many CSS stylesheet inclusions or the CSS style blocks in your <head> tag are too large, these can slow updates too.
You can try switching Telerik RadAjax's head update feature off if you do not load CSS-rich controls in AJAX requests.
You can do that by setting the EnablePageHeadUpdate property to false.
Most browsers render documents a lot slower when operating in quirks mode. Try switching to strict mode by specifying a doctype for your document:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"