ASP.NET AJAX interview question

19. Can we call server-side code from JavaScript?

Yes, page methods and Web services are the two techniques to call the server-side code from JavaScript.

20. What are the components of the ASP.NET AJAX architecture?

You can divide the ASP.NET AJAX architecture into two components – AJAX client architecture and AJAX server architecture.

21. Describe AJAX Control Extender Toolkit.

AJAX Control Toolkit is a set of extenders that are used to extend the functionalities of the ASP.NET controls. The extenders use a block of JavaScript code to add new and enhanced capabilities to the ASP.NET controls. AJAX Control Toolkit is a free download available on the Microsoft site. You need to install this toolkit on your system before using extenders.

22. Explain the need of the Timer control in AJAX.

The Timer control is used with an UpdatePanel control to allow partial-page updates at a specified interval. It is mostly used when a periodically partial-page update for one or more UpdatePanel controls is required without refreshing the entire page.

The Timer control is a server control that sets a JavaScript component in the Web page. The interval property of the Timer control specifies time in milliseconds. Similar to the UpdatePanel control, the Timer control also requires an instance of the ScriptManager control in the Web page.

When the Timer control initiates a postback, the Tick event is raised on the server for which you can provide an event handler to perform the actions when the page is submitted to the server. The Tick event occurs when the time specified in the interval property has elapsed and the page is posted on the server. You can add one or more Timer controls on a Web page. Usually the entire page requires only a single Timer control; however, you can use multiple Timer controls, if the UpdatePanel controls are being updated at different intervals.

23. List the different states of XMLHttpRequest with their description.

The different states of the XMLHttpRequest object are as follows:

Uninitialized – Refers to the state when the object has not been initialized.
Open – Refers to the state when the object has been created; however, the send function has not been invoked.
Sent -Refers to the state when the send function is invoked; however, the status and headers are not available.
Receiving – Refers to the state when the process is receiving data.
Loaded – Refers to the state when the procedure is completed and the entire data is available.
24. Can we nest the UpdatePanel controls?

Yes, we can nest the UpdatePanel control.