If ((e.command = "ADDNEWROW" || e.Learn to use Devexpress ASP.NET controls, and get $250 worth of controls included with the bookĭevexpress is a leading supplier of ASP.NET controls - the addins used in ASP.NET sites. On the server, the PerformCallback method raises the CustomCallback event and passes the specified parameter to the event. You can pass information from the client side to the server as the method’s parameter.
Call this method to send a callback to the server. Send a Custom CallbackĭevExpress controls that support custom callbacks implement the client-side PerformCallback method. On the client, the data is collected by a JavaScript function and used to update the control state (for instance, to display a new page of records). The data is downloaded in the background, invisible to the user. For instance, ASPxGridView sends callbacks to filter, sort, or edit data. For information on how to upload a file on the client, see the following topic: Download a File on the ClientĬomplex DevExpress ASP.NET controls send callbacks to update their own rendering. In this case, client-side objects cannot determine the result that is sent to the browser and their state becomes broken. While the file is downloading, the callback result is cleared and the file content is written to the server response directly. When a callback is sent, a client-side object awaits a proper callback result. You cannot download a file during a callback. You can find different workarounds in the following topic: Update a Control in a Callback of Another Control (Workarounds). You cannot update an external control in a callback of another control.Ī callback result contains only the updated part of a page. Use the IsCallback property to determine whether the page request is the result of a callback. View state information is retrieved and available on the server, but changes made to the state do not persist.Īs a result, less data is sent back to the client and only specific parts of the page is refreshed. The SaveViewState() method is not called.The server runs a modified version of a normal page lifecycle where the following steps are skipped: In callback mode, an action triggers an asynchronous request to be sent to the web server.
The server runs the full page lifecycle and sends the new page markup to the client.
In postback mode, an action submits a web page to the server for processing. The image below demonstrates a simplified diagram of a postback and callback request processes. Page LifecycleĬallbacks reduce the page lifecycle. This reduces the network traffic and response time. The callback result contains only the updated part of a page. Callbacks allow you to call server code asynchronously and obtain the callback result without a postback.
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