Here is code snippet to maintain the scroll position after post back.

Application level

Add the following line in your web.config file or modify the existing one

<pages maintainScrollPositionOnPostBack="true">

Page Level

Add the the following attribute in the page directive of your aspx page

<%@ Page MaintainScrollPositionOnPostback="true"

Code level

Even you set in the code behind file

Page.MaintainScrollPositionOnPostBack = true;