AJAX Helpers in ASP.NET MVC

What are AJAX Helpers?

AJAX helpers are a collection of utility methods and classes in ASP.NET MVC that make it easier to integrate AJAX (Asynchronous JavaScript and XML) capabilities into web applications. These tools make it easier to send asynchronous requests from client-side code to server-side activities and handle responses smoothly.

Unobtrusive AJAX

ASP.NET MVC provides unobtrusive Ajax based on jQuery. The unobtrusive Ajax approach means that you design your Ajax features using helper methods rather than adding blocks of code to your pages.

Various configuration options for AJAX Helpers

The AjaxOptions class offers attributes that allow you to set callbacks at various phases of the AJAX request life cycle. The AjaxOptions class for AJAX helpers provides the following properties:

• Url: The URL to request from the server.
• Confirm: Shows a message in a confirmation dialogue to the user. If the user clicks OK, the AJAX call will proceed.
• OnBegin: Specifies the name of a JavaScript function that is executed at the start of an AJAX request.
• OnComplete: Specifies the name of a JavaScript function that is executed at the end of an AJAX request.
• OnSuccess: Specifies the name of a JavaScript function that is executed when an AJAX request is successful.
• OnFailure: Defines the name of a JavaScript function that is invoked if the AJAX request fails.
• LoadingElementId: The ID of a container that will display a progress message or animation while the AJAX call is running.
• LoadingElementDuration: The time in milliseconds for which the progress message or animation is displayed.
• UpdateTargetId: Specifies the container ID to update with the HTML returned by the action function.
• InsertionMode: Determines how the target container shall be populated. The possible options are InsertAfter, InsertBefore, and Replace (the default).

Cross Domain AJAX

Web browsers by default limit AJAX requests to the same origin to avoid security issues such as XSS attacks. However, if you need to use external APIs (such as Twitter or Google), you must allow JSONP requests or Cross-Origin Resource Sharing. ASP.NET MVC does not support them by default, therefore you'll need to configure and code to enable them.

AjaxOptions Class

AjaxOptions contains a namespace called System.Web.Mvc.Ajax. It also contains an assembly called System.Web.Mvc.dll. It represents the options for launching Ajax scripts in an ASP.NET MVC application. It has its constructor, AjaxOptions(), which creates a new instance of the AjaxOptions class.

AjaxOptions Method

AjaxOptions Methods apply to MVC 5.0. The AjaxOptions Class contains a method named AjaxOptions.The ToUnobtrusiveHtmlAttributes() method returns the Ajax settings as a collection of HTML attributes for unobtrusive JavaScript.