I was wondering on how telerik(RADAjax) controls working, it’s pretty well designed architecture, finally i got an awesome paper from telerik blog! – Here’s you gatta go for it!
How Does RadAjax Do It?
When you execute an Ajax callback using RadAjax (or any RadAjax based controls, such as RadGrid), the framework performs these major actions:
The step in this process that handles updating the page controls is obviously “Update Controls HTML”. If we look at the step in detail, we see it performs the following steps: 
Basically, RadAjax takes the collection of updated controls returned from the server (as defined in your RadAjaxManager or as contained in your RadAjaxPanel) and systematically removes the old version from the page and inserts the new version. To do this, RadAjax must know where a control is located on a page (determined by looking at an element’s parent and nextSibling). Optimizing your updates to minimize these page searches is one of the key ways you can improve your
Ajax performance.Also, they clearly explained how memory leaks can be reduced in the IE. Worth to read it!
Download formatted PDF version for easy reading
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