tailieunhanh - ASP.NET AJAX in Action phần 5

để nhận được nhiều nhất của các phần mở rộng, và bạn cũng có một cái nhìn thoáng qua như thế nào ScriptManager làm việc dưới mui xe. Nhưng bạn vẫn chưa xong. Ngay cả những ứng dụng tốt nhất có sai sót hoặc nâng cao các trường hợp ngoại lệ. | With great power comes great responsibility 195 One of the most fascinating controls in the AJAX framework is the UpdatePanel. This new control replaces the need for a page to refresh during a postback. Only portions of a page designated by the UpdatePanel are updated. This technique is known as partial-page rendering and can be highly effective in improving the user experience. At the end of chapter 1 and in segments of chapter 4 you got a glimpse into how the UpdatePanel works and how simple it is to apply to existing applications. In this chapter the first of two dedicated solely to the UpdatePanel we ll take you through a series of examples that demonstrate how to use the control effectively. In the process you ll gain some insight into how it works together with the ScriptManager control to manage and orchestrate partial-page updates. By the end of this chapter you ll have a solid understanding of how to apply the UpdatePanel correctly to enhance applications. Just like any other powerful tool the UpdatePanel requires care and knowledge to fully exploit its influence on a page s performance and behavior. We begin this chapter with some thoughts on its power and responsibilities. With great power comes great responsibility The most amazing thing about the UpdatePanel is how easy it is to use. With a few lines of code and no client script the behavior of a page is instantly transformed by its presence. If it isn t employed correctly performance and the end-user experience can be diminished. Understanding how to use the UpdatePanel effectively and how and why the control works the way it does is a vital step toward creating superior and more engaging web pages. After you become familiar with the UpdatePanel control it will become one of those tools you can t live without. We liken it to a Tivo or digital video recorder DVR before they came along most of us didn t know what we were missing. Now that we own these appliances we can t .