Ajax learning

1. AJAX = Asynchronous JavaScript and XML.
2. AJAX 是一種在無需重新加載整個網頁的情況下，能夠更新部分網頁的技術。
3. XMLHttpRequest 是 AJAX 的基礎，不管任何ajax技術，這個object用來無縫隙地exchange數據。基本上說，JS用這個object交換xml和text data 在Client和Server之間。

xmlhttp.open("GET","test1.txt",true);
xmlhttp.send();

4. Difference between Synchronous and Asynchronous Postback?

In Synchronous postback, complete web page is sent to server and in return rendering the output (i.e.complete page)

In Asynchronous postback, partial page goes to the server and renders only partial (required)part of the page.

5. What are the basic controls in ASP.NET AJAX?
Following controls can be considered as core AJAX controls in ASP.NET.
  ScriptManager - ScriptManager basically manages all ASP.NET AJAX resources of a web page, creates proxies for asynchronous web service call and also manages partial page updates… etc.
  ScriptManagerProxy
  UpdatePanel - apply partial page update/rendering, we can add one or more UpdatePanel controls
  UpdateProgress
  Timer

Reference: http://www.w3school.com.cn/ajax/ajax_xmlhttprequest_send.asp

http://www.webdevelopmenthelp.net/2014/04/asp-net-interview-questions-part5.html