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It is difficult to find a site on the internet which does not respond to user’s action. By user’s action, i mean to say, clicking on a button, selecting something from a list, navigation links. These are the actions which make the site to respond.

The process is as follows- When you click on a button of the web-page, the site gets connected to the server and calls the appropriate action at server which either introduces some changes to the original web-page or calls a new web-page. As a result,a modified web-page or new web-page is rendered back to the user. This whole process is referred  to as Postback.

In real life, if we go to a bank to withdraw money, we have to fill a simple withdrawal form and give it to the cashier, cashier will write our waiting number on the top and give it back assuming it is correctly filled. This scenario can easily be related to a post back as submitting the form is a user action and in reply to that,cashier modifies the original form by writing a waiting number.

Lets see AutoPostBack, Just we have added the term ‘auto’ here with the postback and made this process partially automatic. How automatic? because there no button clicks required to initiate the postback process. Why partially? because for this process also user intervention is required, although we are saved from any button clicks but still we have to make a selection from any selection list provided. for ex.

List item,ListControl,BulletedList,CheckBoxList,DropDownList,ListBox,RadioButtonList,CheckBox

CrossPagePostBack is also a variant of PostBack . Here the original page is not modified and rendered to user on postback but user is served with a new page, still the values of old page will remain available to the new page. If in the same bank example, we apply for a loan then we have to go to each department and fill out some form in a serial manner. Each next department will already be having our information from the previous department. This is crosspageposting.

Callback is the minified version of postback where only part of the page is sent back and received from the server. This process is initiated by our friend Javascript. Lets see, while roaming between different departments of bank for loan, you want to update something in your application then there is no need to again go back to each department for updation, just go to records department and get information updated in master record.

It was difficult to find a real time scenario for postback, I request you all to help me in improving this article.