Programming ASP.NET 3.5, 4th Edition

The UpdatePanel Control

The majority of the controls you’ve seen thus far in this chapter and in Chapter 4 have had some sort of graphical component. The Panel control does not, nor does the UpdatePanel, which you’ll look at next. Available initially in Microsoft’s ASP.NET AJAX Extensions download and now included directly in .NET 3.5, the UpdatePanel has much the same purpose as the Panel control—to identify and isolate a set of controls on a page—but with a different intention once the controls have been added to the panel.

If you’ll recall from Chapter 3, the UpdatePanel is a server-side control that enables the common AJAX pattern of partial-page updates. Or rather, as well as being able to make the controls it contains visible or invisible, the UpdatePanel lets you isolate content you want to update independently from the rest of the content on the page.

One of the best features of the UpdatePanel is exactly how easy it is to enable this partial-page postback. You just drag one or more UpdatePanel controls onto your page and then drag controls you want updated into the UpdatePanel. Each UpdatePanel is updated individually and asynchronously, without affecting one another or anything else on the page.

Tip

You can disable all UpdatePanels on a page by setting the ScriptManager’s EnablePartialRendering property to false on that page.

It’s time to demonstrate. Add a new AJAX web form to the C5_MoreControls website and call it UpdatePanelDemo.aspx. First, you need to establish what the ...