Building an interactive user interface with Microsoft asp.net Ajax technology-part1

Introduction

Over the past few years, Web developers have started using JavaScript to perform asynchronous postbacks to the Web server, which is to send and receive only the necessary data. These technologies are generally referred to as Ajax. If the design is reasonable, AJAX-enabled Web applications, The high level of interactivity of its user interface is entirely comparable to that of desktop applications.

Because Ajax contains many different layers of technology in the network system (networking stack), it is difficult and error-prone to perform Ajax without using the AJAX framework. Fortunately, Microsoft has launched a free Ajax for ASP.net developers Framework: Microsoft asp.net ajax. This article begins with an overview of Ajax technologies and how to start using Microsoft ASP.net ajax, and then explore specific controls and usage details.

A brief review of Ajax history

The Client-server mode consists of two sides: a client and a server. The server waits for requests from the client, handles the processing, and then responds; The client sends a request to the server, waits for a response, and finally processes the returned data. A Web application is a typical representation of a client-server pattern. On the client-typically a Web browser, requesting a specific resource from a Web server that might be static content, such as an HTML page or a picture, where the server simply needs to return it Or it may be dynamic content, such as a ASP.net page, at which time the server needs to do some processing to return it. However, the interactive mode is the same: the client requests a specific resource, and the server side returns it to the customer.

One drawback of the Client-server model is latency. The client must periodically communicate with the server, update the user to enter information, or obtain the latest data. In this process, the user must wait and waste the request/Response lifecycle time. In a asp.net application, this delay behaves when a postback occurs. The most obvious. Imagine a list of products in an E-commerce site that can be categorized and paged out. However, when you switch to the next page, you will need to generate a postback to the server to get The next page of the product. Naturally, this will produce a delay, from a second to a few seconds, depending on a variety of factors (such as network connection speed, network congestion, server load, database query, etc.).

The main drawback is that page return requires that all page form fields be sent to the server, and the entire page content returned to the browser. As a result, there is too much data to interact with, because we only need information on the next page of the product. Ajax can reduce this latency, The method is to use JavaScript to make an asynchronous postback to the WEB server. These postbacks transmit and receive the smallest amount of required data. For more information on Ajax background, refer to Jesse James Garrett's essay "Ajax:a New approach to Web Applications, in this article he created the term "Ajax".

Many Ajax frameworks are commercial, and of course there are open source libraries (open source libraries). In the first half of 2006, Microsoft released its own AJAX framework, namely: Microsoft ASP.net ajax, The focus of this series of articles.