AJAX in ASP.NET James Crowley Developer Fusion

Overview What is AJAX? How does it work? Using it in ASP.NET 1.x Using it in ASP.NET 2.0 Challenges

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 Parameters

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 Text, XML, HTML, etc

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  “My AJAX.NET”

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

Demo “Google Suggest”

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

Demo AJAX in ASP.NET 2.0

Atlas New library from Microsoft to plug-in to ASP.NET 2.0 Preview available from Warning: pre-Alpha quality! But Microsoft wants your feedback…

Atlas Cross-browser script libraries, bringing namespaces, inheritance, and plenty more Callbacks triggered in similar way to 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 Go away and experiment! me: AJAX enables you to create web apps that are… more responsive with enhanced functionality … and a great user experience

References ASP.NET AJAX Libraries  (AJAX.NET)  (My AJAX.NET)  (Atlas) My Contact Details  Web: 