After reading your chapter on AJAX in your book I am still little bit fuzzy and confused how AJAX and ViewState interact with each other. With AJAX you are supposedly doing Asynchronous partial page postbacks,(is that correct?) but then how does it effect the ViewState data stored in Hex in hidden fields of the browser? Does the ViewState data also get posted back too? Also, does AJAX have any kind of performance benefit as far as the amount of data that is posted back to the server and does using AJAX on your webpages and thereby leaving a smaller footprint on the network server thereby improving performance of your website or it is all just cosmetic to have flicker free webpages?

Thanks once again.

Hi there,

In many cases, the ViewState field is sent back and forth as well and then updated at the client for future post backs.

Quite often, there's a *perceived* performance improvement because flicker is reduced. Whether there's a real performance improvement depends on what you're sending back and forth. You can use tools such as Fiddler to find out the exact data being sent. Typically, you'll be sending fewer bytes (as not the entire page is sent), but at the server the complete page still goes through the page life cycle.

Using web services called from client side code (as explained in the book as well) or also a very interesting choice, and often a better alternative IMO. They give you snappy UI feedback (just as the UpdatePanel), but have much less overhead associated with them.

Cheers,

Imar

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Imar Spaanjaars
http://Imar.Spaanjaars.Com
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Author of Beginning ASP.NET 4.5 : in C# and VB, Beginning ASP.NET Web Pages with WebMatrix
and Beginning ASP.NET 4 : in C# and VB.
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