is it possible to do partial postback on web?

Question

Hi all,

I read some paragraphs in a book saying that it is not possible to do a partial postback for web, even AJAX is employed. Ajax will postback everything and update only ajaxfied controls. However, on pages I made using ajax, I used Fiddler to monitor the transportation. I found when the page initial load, it loaded everything include pictures .... However, when I click a button and do a ajax postback. I can only see the some data were loaded.... Looks like it doesn't need to reload the whole page again. I don't know if what I see is correct? Or the book I read is correct?

Thank you guys.

Answer 1

That depends what you put in the term "postback".

The AJAX call will send the complete form data back to the server, just as if the form was posted normally. The server will answer with a partial response that only contains the parts of the page that should be updated.

So, the request is not partial, but the response is.

Answer 2

I am not sure how you are posting back from the client side. I am guessing you are using UpdatePanels. How well you 'AJAX-ify' a web page depends on what method you employ.

1. UpdatePanels - Read Dave Ward's posting on them - http://encosia.com/2007/07/11/why-aspnet-ajax-updatepanels-are-dangerous/
2. PageMethods to post back to a web service, get the data and update the DOM to display the result
3. JQuery and other such AJAX frameworks to post back to a web service

I am sure the link above should clear things up a bit

Answer 3

I'm having a hard time understanding your terminology. I'm not really sure what a "postback" is, much less a "partial" one. I do know that one of the basic ways to transmit information to an HTTP server is via a POST request, which is usually used when submitting forms. If you mean to say that the entire form is transmitted when you click a submit button, I believe you'd be right.

You also seem to be doing something with AJAX, but it's difficult to tell. The whole point of AJAX is to have dynamic data displayed on a page without resorting to reloading it. Defining what to send and what to do with the results is entirely up to your own JavaScript. So unless you're using a framework, which you don't specify, there is no such thing as "ajaxified controls."

In any case, "AJAX" usually means using the XMLHttpRequest() method of modern browsers to send data to servers without refreshing the page. When you call this function, you specify exactly what data to send. This has nothing to do with HTML forms. One caveat: if you are indeed using a library for AJAX, it might impose additional limits on how you structure information to send.