ASPxAutoCompleteBoxBase.Callback Event

Fires when a round trip to the server has been initiated by a call to the client PerformCallback method.

Namespace: DevExpress.Web

Assembly: DevExpress.Web.v23.2.dll

NuGet Package: DevExpress.Web

Declaration

C#

public event CallbackEventHandlerBase Callback

VB.NET

Public Event Callback As CallbackEventHandlerBase

Event Data

The Callback event's data class is CallbackEventArgsBase. The following properties provide information specific to this event:

Property	Description
Parameter	Gets a string that contains specific information (if any) passed from the client side.

Remarks

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 PerformCallback method.

Specific information passed from the client side can be obtained via the Parameter property.

The necessary actions can be additionally performed on the client side before and after callback processing by using BeginCallback and EndCallback client events.

Note

• If an editor’s 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 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 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.

After the PerformCallback method is called on the client, the Callback event handler is raised during each page postback. You can use the IsCallback property to determine if the PerformCallback method raises the event.

C#

protected void ASPxComboBoxInstance_Callback(object sender, DevExpress.Web.ASPxClasses.CallbackEventArgsBase e) {  
    DevExpress.Web.ASPxEditors.ASPxComboBox cmb = (DevExpress.Web.ASPxEditors.ASPxComboBox)sender;  
    if(cmb.IsCallback) {  
        //Raised by PerformCallback  
    }  
    //else //Raised by Postback  
}  

VB.NET

Protected Sub ASPxComboBoxInstance_Callback(ByVal sender As Object, ByVal e As DevExpress.Web.ASPxClasses.CallbackEventArgsBase)  
    Dim cmb As DevExpress.Web.ASPxEditors.ASPxComboBox = CType(sender, DevExpress.Web.ASPxEditors.ASPxComboBox)  
    If cmb.IsCallback Then  
        'Raised by PerformCallback  
    End If  
    'Else 'Raised by Postback  
End Sub