Define AJAX ,Controls of Ajax how to use Ajax in web application

Define AJAX ,Components of Ajax how to use Ajax:




Define AJAX/What is Ajax?


AJAX stands for “Asynchronous JavaScript and XML”. It’s basically a technique for creating Rich Internet Applications (RIA) that are faster as well as more interactive, using a combination of commonly used techniques as HTML/XHTML, CSS, Document Object Model (DOM), JavaScript, XML/XSLT and XMLHttpRequest object.
XMLHttpRequest object is the key basis of AJAX and makes it possible to communicate with the web server asynchronously and exchange data. As compared to a traditional request which returns a complete web page,  partial web page is returned as response to an AJAX request.

What is ASP.NET AJAX?

Microsoft provided an implementation of AJAX functionality known as ASP.NET AJAX.
As we discussed in above interview question that AJAX is a combination of various techniques, so Microsoft simplified the usage of these techniques with its own implementation. ASP.NET AJAX is a set of extensions to ASP.NET and comes with reusable AJAX controls. Using ASP.NET AJAX, we can develop applications that can update partial page instead of a complete page refresh.
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), whereas in case of Asynchronous postback, partial page goes to the server and renders only partial (required) part of the page.



What are the basic controls in ASP.NET AJAX?

Following controls can be considered as core AJAX controls in ASP.NET.
  1. ScriptManager
  1. ScriptManagerProxy
  1. UpdatePanel
  1. UpdateProgress
  1. Timer


Later more controls are added to ASP.NET AJAX library e.g. Script Loader, Client Data Context, Client Data Access, jQuery Integration etc. For complete reference, look for AJAX Control Toolkit.


ScriptManager Vs ScriptManagerProxy?


As we understand that we can have only one ScriptManager control on a page but we can have multiple ScriptManagerProxy controls.
Consider a scenario that we have ScriptManager in our MasterPage that is available for all content pages. Now, we wanted to register a web service in a particular page. So, we will not add another ScriptManager to that page instead we will add ScriptManagerProxy to it in order to avoid error.

What is the role of UpdatePanel in ASP.NET AJAX?


UpdatePanel is the control that facilitate the partial page rendering functionality in an ASP.NET application. As discussed earlier that using ASP.NET AJAX, we can communicate with a web server asynchronously and update a part of a page without a complete page postback. In order to apply partial page update/rendering, we can add one or more UpdatePanel controls to our ASP.NET Page as follows:
   <asp:ScriptManager ID=”ScriptManager1″ runat=”server”></asp:ScriptManager>
<asp:UpdatePanel ID=”UpdatePanel1″ runat=”server”>
            <ContentTemplate>
                <asp:Label ID=”lblPanel” runat=”server” Text=”Update Panel Added.”></asp:Label><br />
                <asp:Button ID=”btnTestButton”
                                   runat=”server”
                                  OnClick=”btnTestButton_Click”
                                  Text=”Test Button” />
      </ContentTemplate>

    </asp:UpdatePanel>

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