Chapter 25. ASP.NET AJAX
So far, you've learned to build web pages that use the postback model. With the postback model, pages are perpetually being sent back to the web server and regenerated.
For example, consider the greeting card maker you first saw in Chapter 6. When the user picks a font, enters some text, or chooses new colors, the page is posted back to the web server, allowing your code to run. The web page code makes the necessary adjustments, ASP.NET renders the page to HTML all over again, and the browser receives (and displays) the new version of the page.
This process seems somewhat labor intensive, but it's actually not that bad. The time required to complete the whole process (transmitting the posted-back page, running the code, ...