ASP.NET AJAX interview question

13. Explain the limitations of AJAX.

The following are the limitations of AJAX:

  • It is difficult to bookmark a particular state of the application.
  • Function provided in the code-behind file do not work because the dynamic pages cannot register themselves on browsers history engine automatically.
  • If JavaScript is disabled, then AJAX is not able to perform any work.
  • Response time may be slow because different controls of a page are loaded at different time.

14. What are the differences between AJAX and JavaScript?

The differences between AJAX and JavaScript are given as follows:

  • AJAX sends request to the server and does not wait for the response. It performs other operations on the page during that time. JavaScript make a request to the server and waits for response.
  • AJAX does not require the page to refresh for downloading the whole page while JavaScript manages and controls a Web page after being downloaded.
  • AJAX minimizes the overload on the server since the script needs to request once while JavaScript posts a request that updates the script every time.

15. Explain the UpdatePanel control.

The UpdatePanel control specifies the portions of a Web page that can be updated together. As the UpdatePanelcontrol refreshes only a selected part of the Web page instead of refreshing the entire page with a postback, you get more flexibility to create rich and client-centric Web applications.

Refreshing a selected part of the Web page is referred as partial-page update. You can add one or more UpdatePanelcontrol in the Web page, which automatically participates in partial-page update without custom client script. TheUpdatePanel control uses the UpdatePanel class to support the partial-page rendering.

16. What does the DynamicPopulateExtender control do?

The DynamicPopulateExtender control populates the contents of a control dynamically. It enables you to send an asynchronous call to the server that dynamically populates the contents of a control. TheDynamicPopulateExtender control replaces the contents of a control with the result of a Web service or page method call.

17. What does the MinimumPrefixLength property of the AutoCompleteExtender control do?

The MinimumPrefixLength property sets the minimum number of characters that must be entered before getting suggestions from the Web service.

18. What is the importance of client-side libraries?

Client-side libraries contain built-in code to make asynchronous calls over XMLHTTP. These libraries automatically handle browser compatibility issues. These libraries are based on a programming model similar to ASP.NET.

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