Long time ASP.NET Webforms developer, new to Ajax development (mostly via the UpdatePanel control !).
Since no postbacks are happening the server does not reset the
As GenericTypeTea commented, there are server side postbacks when using .NET AJAX with UpdatePanel. The only difference is that the entire page is not loaded. All the server side code is triggered as normal, but the information is sent between the server and the page in a different way using the AJAX technology.
You can even call server side methods from client side javascript using a mechanism that .NET calls PageMethods. This is a more "manual" way of using AJAX in .NET than the traditional UpdatePanel technique.