asp.net upc-a reader

asp.net upc-a reader

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Figure 34-11. Security settings In the Security Tokens Managers section, click the Add button. This displays the SecurityToken Manager dialog box (see Figure 34-12).

The ingredient you can use with Atlas controls is behaviors, which are predefined bits of functionality you can attach to other HTML elements. Behaviors are triggered by client-side events and then can update properties, call methods, or provide complex functionality such as autocompletion in text boxes. Of course, you can also create your own behaviors but because they tend to be quite complex, the chief benefit is reusing the prebuilt behaviors that Microsoft and other third parties develop. Table 35-3 lists the behaviors that Atlas includes. Table 35-3. Behaviors

This example is extremely practical. However, before you start using the DynamicPanel in your applications, you might want to consider a more mature sample by Bertrand Le Roy that uses the same technique but adds a fair bit of extra frills (and a lot more code). To check it out, surf to http://www.gotdotnet.com/ workspaces/directory.aspx, and search for RefreshPanel. You ll also see a similar control that s included with Atlas in the following chapter.

Note that the order of change events is nondeterministic, and you shouldn t rely on these events occurring in any set order. However, you re likely to see events raised in the order in which the controls are declared. The only detail of which you re guaranteed is that all the change events fire before the ServerClick event that triggered the postback.

Allows you to show a drop-down list of suggestions under a text control as the user types Performs an action when the user clicks the element to which the behavior is attached Performs an action when the mouse pointer enters or leaves the bounding box of the element to which the behavior is attached Displays a pop-up element overtop of a portion of the page Provides a busy indicator for long-running operations and disables all controls while the operation is underway

Summary

HTML server controls provide a relatively fast way to migrate to ASP .NET but not necessarily the best way. For one thing, the names of HTML controls and their attributes are not always intuitive, and they don t have the same design-time support for attaching event handlers. The HTML controls also have certain limitations, such as that style properties must be set through CSS syntax (which is more difficult than setting a direct property) and that change events can t be raised until the page is posted back in response to another action. Finally, HTML server controls can t provide user interface elements that aren t already defined in the HTML standard. If you want to create some sort of aggregate control that uses a combination of HTML elements to render a complex interface, you re on your own. To address these issues, ASP.NET provides a higher-level web control model. All web controls are defined in the System.Web.UI.WebControl namespace and derive from the WebControl base class, which provides a more abstract, consistent model than the HTML server controls. Web controls also enable additional features, such as automatic postback. But the really exciting part is that many extended controls don t just map a single HTML tag but instead generate more complex output made up of several HTML tags and JavaScript code. Examples include lists of check boxes, radio buttons, calendars, editable grids, and so on. Figure 4-6 shows a portion of the inheritance hierarchy for web controls.

The following example demonstrates HoverBehavior and PopupBehavior. The page includes a piece of underlined text (in this case, the word Atlas). When you hover over this text, a pop-up box with several links appears, as shown in Figure 35-12.