Instantiating an object of a server-side class in client-side JavaScript

Sorry this might be an easy question, but I couldn't find how to do this.

I want to define an object like,

var myObj = new MyServerSideClass();

MyServerSideClass is defined in the cs code. Is this possible? If it is, how? Thanks in advance.

Checkout the Example of Passing and Returing Complex Types in this doc:
http://www.asp.net/AJAX/Documentation/Live/tutorials/ConsumingWebServicesWithAJAXTutorial.aspx