I couldn't get MaintainScrollPositionOnPostback to work for me no matter what I tried. Based on Darkseal's answer and Eirik H's comment, I tried the following code which worked for me. This will only work if you have an ASP.NET ScriptManager (i.e. MicrosoftAjax.js) on your page. You also need JQuery added to your page. Add the below code to your .aspx file somewhere underneath asp:ScriptManager tag.
<asp:HiddenField runat="server" ID="hfPosition" Value="" />
<script type="text/javascript">
$(function () {
var positionField = $("#<%=hfPosition.ClientID%>");
window.onscroll = function () {
var position = $(window).scrollTop();
positionField.val(position);
};
});
function pageLoad() {
var positionField = $("#<%=hfPosition.ClientID%>");
var position = parseInt(positionField.val());
if (!isNaN(position)) {
$(window).scrollTop(position);
}
};
</script>
Basically we are holding the scroll position inside the value of a hidden field called hfPosition. Whenever the page is scrolled, the value will be updated. Then when a postback happens pageLoad() will automatically be called and will get the value of hfPosition and scroll to that value.
Including the ScriptManager and JQuery, my final code snippet looked something like this:
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<script src="../Scripts/jquery-3.3.1.min.js" type="text/javascript"></script>
<asp:HiddenField runat="server" ID="hfPosition" Value="" />
<script type="text/javascript">
$(function () {
var positionField = $("#<%=hfPosition.ClientID%>");
window.onscroll = function () {
var position = $(window).scrollTop();
positionField.val(position);
};
});
function pageLoad() {
var positionField = $("#<%=hfPosition.ClientID%>");
var position = parseInt(positionField.val());
if (!isNaN(position)) {
$(window).scrollTop(position);
}
};
</script>/>