ICallbackEventHandler Interface
Used to indicate that a control can be the target of a callback event on the server.
Assembly: System.Web (in System.Web.dll)
The ICallbackEventHandler type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | GetCallbackResult | Returns the results of a callback event that targets a control. |
![]() | RaiseCallbackEvent | Processes a callback event that targets a control. |
Implement the ICallbackEventHandler interface for any custom control that needs to receive callback events. For more information, see Implementing Client Callbacks Programmatically Without Postbacks in ASP.NET Web Pages.
Examples of controls that implement the ICallbackEventHandler interface include the GridView, DetailsView, and TreeView controls. When a callback event targets a control that implements the ICallbackEventHandler interface, the RaiseCallbackEvent method is called to handle the event, passing the event argument as a parameter and the GetCallbackResult method returns the result of the callback.
Controls that retrieve data from a data source control during callback can do so synchronously or asynchronously. ASP.NET controls like GridView, DetailsView, and TreeView are implemented synchronously. Synchronous callbacks do not prevent the user from working in the browser. In synchronous mode, only one callback at a time can execute, with the last callback taking precedence. When a Web control is implemented to support asynchronous behavior, multiple callbacks can be raised simultaneously. For details on asynchronous programming, see Asynchronous Programming Design Patterns.
You can specify whether callback events originating from the user interface rendered by a control implementing the ICallbackEventHandler interface are validated. Validation of events is a good security practice. However, for performance reasons you can disable it. To control whether event validation is performed on callback events, set the enableEventValidation attribute of the @ Page directive or the enableEventValidation attribute of the pages Element (ASP.NET Settings Schema) of the Web.config file. If you set the EnableEventValidation property in code, set it in the Page_Init phase of page processing. For more information on balancing the security benefit of event validation with its performance cost, see ASP.NET Performance Overview.
| Topic | Location |
|---|---|
| Client-Callback Implementation (Visual Basic) Example | Building ASP .NET Web Applications |
| Client Callback with Validation Implementation Example | Building ASP .NET Web Applications |
| How to: Implement Callbacks in ASP.NET Web Pages | Building ASP .NET Web Applications |
| Client-Callback Implementation (C#) Example | Building ASP .NET Web Applications |
| Implementing Client Callbacks Without Postbacks in ASP.NET Web Pages | Building ASP .NET Web Applications |
| Client-Callback Implementation (Visual Basic) Example | Building ASP .NET Web Applications |
| Client-Callback Implementation (C#) Example | Building ASP .NET Web Applications |
| Implementing Client Callbacks Without Postbacks in ASP.NET Web Pages | Building ASP .NET Web Applications |
| Client Callback with Validation Implementation Example | Building ASP .NET Web Applications |
| How to: Implement Callbacks in ASP.NET Web Pages | Building ASP .NET Web Applications |
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
