Calling Server side function using Ajax

Here is some links that shows working with call server side function using Ajax.

(1) Calling ASP.NET server side method via JQuery - Stack Overflow

(2) Using jQuery to directly call ASP.NET AJAX page methods | Encosia

(3) How to call Server Side function from Client Side Code using PageMethods in ASP.NET AJAX

(4) Call non-static method in server side(aspx.cs) from client side use javascript (aspx)..... - Stack Overflow

(5) Call ASP.net MVC Server side function using Jquery Ajax