Need guidance on handling issues with delta updates in ASP.NET AJAX

[Alex]

Hey everyone, I'm working on an ASP.NET AJAX project and am having some confusion about handling delta updates within partial postbacks.

Specifically:

• I'm trying to update just a small part of a control using delta logic, but the entire control seems to refresh instead.
• I'm not sure if I'm missing a required setting on the UpdatePanel or if delta updates require a different approach in Telerik controls.
• If anyone has best practices, examples, or even "don't do this" warnings, I would seriously appreciate the help.

I am waiting yours valuable replies. Thanks in advance!

[Attila Antal]

Hi Alex,

Delta updates, in the sense of updating only the changed parts of a control (like DOM diffing in Blazor or SPA frameworks), are not supported in ASP.NET Web Forms or Telerik UI for ASP.NET AJAX. Here’s how partial postbacks work and what you can do:

How Partial Updates Work in ASP.NET AJAX:

• Partial updates refresh the entire HTML content of the targeted control or panel, not just the changed portion.
• UpdatePanel (from Microsoft) and Telerik’s RadAjaxManager/RadAjaxPanel both operate this way: after a partial postback, the full markup of the specified control or region is sent to the client.

Best Practices and Warnings:

• You cannot update only a small part of a control using delta logic. The whole control or panel you target will be re-rendered.
• For AJAX in Telerik UI, use either RadAjaxManager or RadAjaxPanel for a set of controls—do not mix them for the same controls.
• To minimize payload and improve performance, keep your update regions as small as possible (e.g., update only the panel or control that needs to change).

Telerik AJAX Example:

<telerik:RadAjaxManager ID="RadAjaxManager1" runat="server" DefaultLoadingPanelID="RadAjaxLoadingPanel1">
    <AjaxSettings>
        <telerik:AjaxSetting AjaxControlID="RadButton1">
            <UpdatedControls>
                <telerik:AjaxUpdatedControl ControlID="Panel1" />
            </UpdatedControls>
        </telerik:AjaxSetting>
    </AjaxSettings>
</telerik:RadAjaxManager>

• This setup will refresh the entire Panel1 when RadButton1clicked (triggers an AJAX request).

If You Need True Delta Updates:

• ASP.NET Web Forms cannot provide delta updates like modern SPA frameworks.
• Consider migrating to ASP.NET Core with Blazor or using a SPA approach if you need minimal DOM changes and more efficient updates.

Further Reading:

• https://msdn.microsoft.com/en-us/library/bb398874.aspx
• https://www.telerik.com/products/aspnet-ajax/documentation/getting-started/on-ajax-and-telerik-ajax
• https://www.telerik.com/products/aspnet-ajax/documentation/knowledge-base/ajax-understanding-ajax-controls 
• http://blogs.telerik.com/aspnet-ajax/posts/13-03-21/different-ways-to-make-a-request-to-the-server

Let me know if you have a specific scenario or control in mind, and I can provide more tailored guidance or examples.

Regards,
Attila Antal
Progress Telerik