what is the use of callback in asp.net?

Question

Hi Tell me the use of callback in asp.net. Can u give me the real time examples to understand the concept clearly. Kindly give me the solution for this problem.

Abhijit Patil · Answer

hey prabu please see the below link which will help for u to understand the details concept of Callback i asp.net http://www.codeproject.com/Articles/12294/Client-side-callbacks-in-ASP-NET-2-0 http://www.codeproject.com/Articles/8218/Client-Callbacks-in-ASP-NET-2-0 hope it helps Regards Abhijit Patil http://dotnetbyabhipatil.blogspot.in

Anurag Sarkar · Answer

A Postback occurs when the data (the whole page) on the page is posted from the client to the server..ie the data is posted-back to the server  and thus the page is refreshed (redrawn)...think of it as ' sending the server the whole page (asp.net) full of data '. On the other hand a callback is also a special kind of postback  but it is just a quick round-trip to the server to get a small set of data (normally) and thus the page is not refreshed unlike with the postback...think of it as ' calling the server and receiving some data back ' With Asp.Net the ViewState is not refreshed when a callback is invoked  unlike with a postback. The reason that the whole page is posted with ASP.Net is because ASP.Net encloses the whole page in a with a post method  and so when a submit button is clicked in the page the form is sent ot the server with all of the fields that are in the form...basically the whole page itself If you are using FireBug (for Firefox) you can actually see callbacks being invoked to the server in the Console . That way you will see what specific data is being sent to the server ( Request ) and also the data the server sent you back ( Response ) Below Image describes it :- Implementing Client Callbacks Programmatically Without Postbacks in ASP.NET Web Pages http://msdn.microsoft.com/en-us/library/ms178208.aspx