The DevExpress ASP.NET Callback Panel (ASPxCallbackPanel) is a lightweight web control that allows you to dynamically update its content via callbacks, preventing undesirable whole page postbacks. You can initiate an update callback by calling the PerformCallback client method.
ASPxCallbackPanel content remains visible while its callback is being processed on the server. During callback processing, the panel control is covered with a customizable Loading Panel and Loading Div elements. The appearance of the Loading Panel can be defined via the LoadingPanelImage, LoadingPanelImagePosition, LoadingPanelStyle and LoadingPanelText properties. The Loading Div's style is customized using the LoadingDivStyle property.
In this example, ASPxCallbackPanel is used to display detail information on an employee selected within a list box. When the selected item in the list box is changed, ASPxCallbackPanel's PerformCallback client method is called to initiate a callback to update the panel content. On the server side, the selected list item's value is used as an SQL SELECT query parameter's value, and as a result, ASPxCallbackPanel displays the requested information.