Fires when a round trip to the server has been initiated by a call to the client ASPxClientComboBox.PerformCallback method.
NuGet Package: DevExpress.Web
public event CallbackEventHandlerBase Callback
Public Event Callback As CallbackEventHandlerBase
The Callback event's data class is CallbackEventArgsBase. The following properties provide information specific to this event:
|Parameter||Gets a string that contains specific information (if any) passed from the client side.|
The Callback event allows you to perform any desired server-side processing and update the editor’s content, if required, in response to a call to the client ASPxClientComboBox.PerformCallback method.
Specific information passed from the client side can be obtained via the CallbackEventArgsBase.Parameter property.
The necessary actions can be additionally performed on the client side before and after callback processing by using the ASPxClientComboBox.BeginCallback and ASPxClientComboBox.EndCallback client event.
- If an editor’s ASPxClientComboBox.PerformCallback method is called on the client, the Callback event will be generated on the server side on each callback request performed by the editor (or on the entire page’s postback).
- The ASPxComboBox control allows you to modify the ASPxAutoCompleteBoxBase.Items collection on callbacks only (e.g., add and remove items, populate ASPxComboBox controls with new data from a data source, etc.).
- The Callback event handler allows changing the control’s value/selection only on a callback that is caused by the ASPxClientComboBox.PerformCallback method. If the event is caused by internal callbacks (loading items on scrolling / items filtering), the control stops selection changing.
- It is not possible, for example, to modify a column collection, change item selection, or change SelectionMode on callbacks. To perform these actions on the client side, you can wrap the control with the ASPxCallbackPanel control and process the required scenario on a callback to the panel.