The DevExpress ASP.NET MVC RoundPanel extension has the capability to load panel content on demand via callbacks.
The CallbackRouteValues property allows you to define the callback routing logic by specifying the names of a Controller and an Action which should handle RoundPanel callbacks. If the callback routing logic is defined, a collapsed panel's content is loaded on initial panel expansion. Otherwise, a collapsed panel's content is loaded with the web page load. Using postponed loading of panel content, you can improve the response time of your web page on its initial load.
A round panel's content can be updated on demand programmatically, using the client-side PerformCallback method.
Note that in this example, callback processing is intentionally paused on the server side for two seconds in order to make the Loading Panel visible during this time.
Local Copy of this Demo
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You can open a local copy of this online demo directly from this webpage (if using v20.2.8, 21.1.4 or higher).
The source code files for this demo are installed (by default) in the following directory:
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\Users\Public\Documents\DevExpress Demos XX.X\Components\ASP.NET\CS\MVCxMultiUseExtensionsDemos