ASP.NET Ajax - Asynchronous Communication Layer Overview

enable the browser to communicate asynchronously with a server using HTTP or HTTPS. There is a clear separation between the business and data tiers on the server and the presentation tier on the client. The browser can have full control of the presentation tier thus providind a rich and responsive user interface, while the server performs the business and data tier tasks.

The asynchronous communication layer offers the following feature set:

It can invoke methods in Web services implemented as .asmx files.

It can invoke specifically enabled ASP.NET page methods as if they were Web service methods.

It can enable and disable the ability to call Web services or specifically enabled page methods from Microsoft ASP.NET AJAX applications.

It supports a variety of serialization formats for passing data between the browser and the server, including:

• JavaScript Object Notation (JSON) as a serialization standard for passing data between the browser and the server. This includes JSON serialization for common .NET data types and extensibility for custom JSON serializers.
• 
  String data.
  
• Custom formats that are processed depending on content type that you can specify.

It can optimize Web service interactions by pre-loading and caching JavaScript proxies. The Microsoft ASP.NET AJAX allows the browser to call ASP.NET Web services using JavaScript. It does so by generating a JavaScript proxy that the client uses to communicate with the Web services on the server. For more information, see How To: Call a Web Service from JavaScript..

It provides extensibility points for using different client executors. An executor is the asynchronous communication layer component that functions as an interface between a client Web request and the network or other media. The executor is the key component that makes possible asynchronous communication between client and server. For more information, see XMLHttpExecutor Class. You can write your own executor that plugs into the asynchronous communication layer.

It can be used with Medium trust.