How to Maintain Scroll Position After Postback in ASP.NET WebForms

In ASP.NET WebForms, when a postback occurs, the page typically reloads, causing the browser to reset the scroll position to the top of the page by default. However, there are scenarios where you might want to maintain or set a specific scroll position after a postback. In this blog post, we'll explore two methods to achieve this: using JavaScript and the MaintainScrollPositionOnPostBack property.

Method 1: Using JavaScript

JavaScript provides a straightforward way to save and restore the scroll position before and after a postback.

Step 1: Add Hidden Field and JavaScript Function

First, add a hidden field to store the scroll position value and a JavaScript function to save the scroll position before the postback.

<asp:HiddenField ID="scrollPosition" runat="server" />
<script type="text/javascript">
    function SaveScrollPosition() {
        var scrollTop = window.pageYOffset || document.documentElement.scrollTop;
        document.getElementById('<%= scrollPosition.ClientID %>').value = scrollTop;
    }
</script>

Step 2: Register JavaScript Function

Register the JavaScript function to execute before the postback, typically on the client-side click event of a button.

<asp:Button ID="btnPostBack" runat="server" Text="Postback" OnClientClick="SaveScrollPosition();"
    OnClick="btnPostBack_Click" />

Step 3: Restore Scroll Position on Postback

In the server-side code, retrieve the scroll position from the hidden field and register a startup script to scroll the window to that position.

protected void Page_Load(object sender, EventArgs e)
{
    if (IsPostBack)
    {
        string scrollValue = Request.Form[scrollPosition.UniqueID];
        ScriptManager.RegisterStartupScript(this, GetType(), "SetScrollPosition", "window.scrollTo(0, " + scrollValue + ");", true);
    }
}

Method 2: Using MaintainScrollPositionOnPostBack Property

ASP.NET WebForms provides a built-in property MaintainScrollPositionOnPostBack to maintain the scroll position automatically after a postback.

Step 1: Set MaintainScrollPositionOnPostBack Property

Set the MaintainScrollPositionOnPostBack property to true in the Page directive of your ASPX page.

<%@ Page MaintainScrollPositionOnPostback="true" %>

Step 2: Implement Postback Logic

Implement the postback logic in your code-behind file as usual.

protected void btnPostBack_Click(object sender, EventArgs e)
{
    // Handle postback logic here
}

Maintaining the scroll position after a postback enhances user experience, especially in scenarios involving long pages or forms. By using either JavaScript or the MaintainScrollPositionOnPostBack property, you can ensure that users stay at the same position on the page even after interacting with server-side controls. Choose the method that best fits your requirements and enjoy smoother navigation in your ASP.NET WebForms applications.