Measure the test taker's understanding about AJAX applications and ASP. NET Atlas Framework.

Measure the test taker's understanding about AJAX applications and ASP. NET Atlas Framework.

I. Introduction

AJAX describes a cross-platform, Client-centric web application development path. In AJAX technology, program developers use Client scripts to call servo applications, in addition, this call uses an XML-based communication protocol. The Microsoft code "Atlas" is an application of AJAX development methods and the expansion of ASP. NET kit. This topic describes the topics related to Web application development to be solved by AJAX, explains basic AJAX concepts, and introduces ASP. NET Atlas is a major revolution and enhancement brought about by AJAX development.

Development issues for AJAX

Both users and developers can experience the limitations caused by the traditional webpage application Request-Response mode. Because the webpage is stateless, whenever the webpage data or user interface needs to be changed, the whole web page must be post back to the Server for update, meaning that the page must be round-trips between the Client and the Server, especially when there is a large amount of data between the Client and the Server, the user will feel a long wait.

Another issue is that HTML controls in Web browsers are limited compared with Rich UIS in desktop applications. Many browsers contain enhanced HTML controls, however, these enhanced HTML controls are implemented for specific browsers. To obtain the Rich UI of these enhanced HTML controls, web application developers must create applications for specific browsers, this will be very complex, so many developers avoid building features with specific Client features in their web pages, therefore, users find that web applications are much less attractive than other types of applications. The AJAX development method provides solutions for the above two development topics.

Ii. AJAX technical concepts

AJAX is built on a core concept: the use of asynchronous calls, combined with XML transmission of data and a large number of use of Client scripts.

In AJAX technology, program developers can use the Client-side Scripts method to call Web Services asynchronously through XMLHTTP, the XMLHTTP communication protocol is often used to encapsulate information into XML data types for transmission across networks. Most browsing operations are implemented as XMLHTTP types, this type is used to create a proxy object for remote call and data sending and receiving. It is called asynchronously. The data on the webpage and the user interface do not need to be round-trips between the Client and the Server, the result is less data transmission and better application efficiency. asynchronous calls can make Web applications more responsive, because the user can continue working in the Client browser while the call is still performed on the Server.

On the other hand, AJAX uses a large number of Client scripts, especially JavaScript, which are used for remote calls, processing Client applications, and establishing enhanced user interface functions.

The AJAX Solution uses JavaScript and works with several other Client-side technologies, including:

· Document Object Model (DOM) in the browser: DOM presents these elements into standard Object groups (such as document and windows) in HTML webpages ), they can also be operated programmatically.

· Dynamic HTML (DHTML): when users input data on pages, DHTML extends the HTML interaction response capability through the Client Script and makes it easier, and does not require round-trip behavior.

· Behavior (Behaviors): This is a programmatic action encapsulated in the user interface (such as dragging drag and drop behavior) and can be linked to web page elements.

· Component: a custom JavaScript Object that can expand the features of Client user interfaces.

By combining these Client technologies, JavaScript enables program developers to build user interface features comparable to those of desktop applications. There are two examples for your reference:

· Microsoft Virtual Earth website: a website that provides electronic maps.

· Microsoft Outlook Web Access: a Client interface for sending and receiving e-mail via a WEB browser.

Both demonstrate the rich user interfaces and high-performance application models built with AJAX technology.

However, using these technologies to construct AJAX applications is complicated. Until now, the program developers still have to manually create the details required for event processing, message transmission, and rich user interfaces. In addition, JavaScript is not an object-oriented language (OOP), so it does not have the features of strong types, namespaces, exception event processing, and OOP. For these features, program developers often have to write the exclusive infrastructure program code built in it in other languages.

Iii. ASP. NET Atlas provides a new way

ASP. NET. The answer to how Microsoft can leverage the power of AJAX applications is: "Atlas", ASP. NET Atlas provides all AJAX capabilities, but it further expands its concept and significantly reduces the complexity of AJAX application development. Atlas also provides both Client and Server capabilities, description:

(1) Client Side

 

Atlas provides a rich set of Script Libraries and provides the following features:

· Object-oriented development

· The Libraries function library on the Client adds object-oriented features to JavaScript, such as type systems, data types, namespaces, and events, these features give program developers a familiar program writing mode, allowing you to develop higher quality, maintainability, and reusable program code.

· Browser compatibility

· The Libraries library automatically handles compatibility issues with different browsers, eliminating the need to write Scripts for specific browsers.

· Behavior and Client components

· The Libraries library includes common behaviors, including "auto-completion, drag and drop, popup, and mouse hovering", and also includes components that can fasten data, this simplifies the establishment of event-driven commercial applications.

· Program code responsible for handling remote calls

· The Libraries library is responsible for managing the complexity of asynchronous calls over XMLHTTP, reducing the need for several lines of Script code for asynchronous calls.

· Declarative program writing mode

· The Libraries function library allows you to use the declarative syntax when creating an Atlas component, just as you do when creating an ASP. NET Server Control.

(2) on the Server side

Atlas also includes a wide range of Servo component features on the Server side to supplement the shortcomings of Atlas in the Client Script Libraries library, including:

· Web server controls

· These ASP. NET Atlas server controls can send Client scripts so that you can use the features of Atlas. If you are very familiar with servo program development, these server controls will be very useful to you, alternatively, you do not have to manually create the Atlas Client Scripts.

· Web Services

· Some Web services can add very useful servo functions to Atlas applications, such as ASP. NET 2.0 profiles.