In ASP.NET 2.0 it is possible to invoke server events from client side script without posting back the page. This is supported through a new mechanism called script callbacks. For more information on this technology, read Dino Espositio’s excellent “Cutting Edge” article on the subject.
Mostly out-of-band calls have been used with fairly simple return values such as strings and numerals. The “advanced” uses have typically been passing arrays as comma separated lists. This has greatly limited the applicability of the technology and created a wide functionality gap between the object oriented programming environment of the server world and the more primitive environment in the browser…
One of the most celebrated classes in the .NET framework is the XmlSerializer class. This class enables you to serialize objects into XML documents and deserialize XML documents into objects. As we all know, XML documents are represented as strings, so it is simple to pass an XML document as either a parameter or a return value on an out-of-band call.