JSON objects representations are small and lightweight compared to XML they are now the core of AJAX.net services serialization. in AJAX.net they work out of the box
you can serilaize/deserialize your objects to JSON using this snippet of server side code
using System.Web.Script.Serialization;
JavaScriptSerializer jss = new JavaScriptSerializer();
//Serialize
jss.Serialize(object);
//Deserialize
yourCustomType result = jss.Deserialize(yourJSONString);
and on the client side you can do the same as long as you have a script manager in your page
// Serialization
var jsonString= Sys.Serialization.JavaScriptSerializer.serialize(JSObject);
//deserialization
var JSObject= Sys.Serialization.JavaScriptSerializer.deserialize(jsonString);