AJAX in ASP.NET

AJAX in ASP.NET
James Crowley
Developer Fusion
http://www.developerfusion.co.uk/

Overview
 What is AJAX?
 How does it work?
 Using it in ASP.NET 1.x
 Using it in ASP.NET 2.0
 Pros & Cons

What is AJAX (and who cares?)
 Current postback solutions can be slow
and confusing to users
 AJAX allows server-side processing to
occur without a postback, and therefore...
a more interactive & responsive UI
 Nothing new, but all the rage thanks to
Google Maps, Flickr, and A9 to name a
few

How it works
Server
Web Server
Database
Client Browser
JavaScript
DHTML
XML HTTP
Object
1
Async HTTP Request

How it works
Server
Web Server
Database
Client Browser
JavaScript
DHTML
XML HTTP
Object
2

How it works
Server
Web Server
Database
Client Browser
JavaScript
DHTML
XML HTTP
Object
3
Async HTTP Response

AJAX in ASP.NET 1.x
 Either we deal with the XML HTTP
request ourselves
 or we can use an existing library, such as
AJAX.NET wrapper
http://ajax.schwarz-interactive.de/
“My AJAX.NET”
http://jason.diamond.name/weblog/

Demo
 “Colourizing” Code

Complex Data Types
 Need to either reproduce (a subset of) the
.NET type system within JavaScript or
vice-versa
 Need to serialize for transfer via HTTP
 Serializable return types dealt with
automatically
 Parameters are harder

AJAX in ASP.NET 2.0
 Known as “Script Callbacks”
 Call ClientScript.GetCallBackEventReference to
get the string for a javascript call to trigger a
callback
 Implement the ICallbackEventHandler interface
public interface ICallbackEventHandler {
void RaiseCallbackEvent(string eventArgument);
String GetCallbackResult();
}
public string GetCallbackEventReference(System.Web.UI.Control control,
string argument, string clientCallback,
string context, string clientErrorCallback, bool useAsync)

ASP.NET 2.0 vs AJAX.NET
 No dynamic mapping of parameters using
reflection
 More complicated with multiple callbacks
 No JavaScript objects corresponding to
server-side types (only returning strings)
 Executes within the page lifecycle

Things to note
 ViewState not updated during a callback
because of allowance for parallel callbacks
 Page.IsPostBack is true for callbacks and
postbacks. Use Page.IsCallback
 Request.Browser.SupportsCallback

Atlas
 New library from Microsoft to plug-in to
ASP.NET 2.0
 Preview available from http://atlas.asp.net/
 Warning: Not yet even Beta quality!
 But Microsoft wants your feedback…

Atlas
 Cross-browser script libraries
 Callbacks can be triggered in same way as
AJAX.NET library
 Web Services integration
 Declarative data binding
 New AJAX-enabled server controls

Things to watch out for…
 Debugging is a pain
 Response timeouts and server exceptions
 Non-JavaScript/non-ActiveX scenarios

Things to watch out for…
 Accessibility, page flow, scroll position
 Can break layered architectures
 Inability to access by URL, and breaking
back/forward browser buttons
 No search indexing for AJAX’ed data

Wrapping Up
 More work for us
 But… fast interactive UI for the user
 Any questions?

References
 ASP.NET AJAX Libraries
 http://ajax.schwarz-interactive.de/ (AJAX.NET)
 Tutorial @ http://www.developerfusion.co.uk/show/4704/
 http://jason.diamond.name/weblog/ (My AJAX.NET)
 http://atlas.asp.net/ (Atlas)
 My Contact Details
 Web: http://www.developerfusion.co.uk/
 Email: james@developerfusion.co.uk

AJAX in ASP.NET

More Related Content

What's hot (20)

Similar to AJAX in ASP.NET (20)

Recently uploaded (20)

AJAX in ASP.NET