Web Parts that require long loading time might significantly slow down the overall page performance by increasing the page load time.
This is especially true with SharePoint search web parts, web parts that interact with third party web services, web parts that deal with large SharePoint lists, etc…
The Asynchronous Web Part framework enables web parts to load asynchronously.
To load pages asynchronously element by element facebook-style to speed up the first display of the page the first choice would probably not be UpdatePanel as it is meant for partial page updates as opposed to partial page loads. Web parts using Asynchronous
Web Part Framework can in fact leverage the UpdatePanel for partial page updates as well.
Web Parts that utilize the Asynchronous Web Part Framework support all the features of SharePoint web parts such as editor web part, web part connections etc…
The Asynchronous Web Part Framework can be applied to existing web parts with very few code changes.
The same framework can also be used for developing web parts for use in Asp.Net applications. (With few file and path changes to replace the SharePoint layouts folder)
As soon as the page is loaded, the web part loads and displays a spinner icon.
Then the web part properties, web part connection information are sent to the web part web service asynchronously and the HTML mark is them loaded into the web part asynchronously.