Before asynchronous mechanism in web development, huge
transfer of data over network and slowness was a big problem. Later we got the way
to send only a required portion of page to server and get it updated in webpage
without flicker (by AJAX). As a web developer you know that it requires writing
code in Java Script and it is not easy for all. As Microsoft always focus to
provide end-user easy-accessibility they built a readymade Update Panel by
putting AJAX mechanism behind the scene which can be used without writing any manual
java script / AJAX code.
Update Panel are created to make the easy use. So we minimize
the use of Postback and at the completion of an asynchronous call/request, a
Callback take care. Though Update Panel may not so good in terms of performance
compared to web methods/JSON, it is used much than them.
Note that we can
overcome this issue by handling Update Panel with Java Script or jQuery.
Avoid overuse Update Panel; But with writing/handling by your
own Java Script/jQuery.