The ASPxCallbackPanel control represents a container area whose content can be updated using an AJAX-based callback technology. The collection of the ASPxCallbackPanel's child controls can be accessed via the ASPxPanelContainerBase.Controls property.
The ASPxCallbackPanel control implements a comprehensive client-side and server-side functionality to enable updating its content on demand via callbacks. The client-side object model contains the client object for the ASPxCallbackPanel control (ASPxClientCallbackPanel), its method required to send a callback to the server (ASPxClientCallbackPanel.PerformCallback), and methods allowing specific client operations to be performed when a callback sends to, and comes from the server side (CallbackClientSideEventsBase.BeginCallback and CallbackClientSideEventsBase.EndCallback). A handler for the available client-side events can be assigned by using the control's ASPxCallbackPanel.ClientSideEvents property. An instance of the ASPxClientCallbackPanel object can be easily identified on the client by using the client programmatic identifier set via the ASPxPanelBase.ClientInstanceName property.
The required server-side processing of a callback sent from the client side by using the ASPxClientCallbackPanel.PerformCallback method can be performed in a handler of the control's server-side ASPxCallbackPanel.Callback event.