What is the difference between postback, autopostback and callback?

can you define autopostback and postback and it's differences and which web server control support autopostback and postback and also the difference betwe开发者_Go百科en postback and callback?

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• postback: the page performs a POST request to itself
• autopostback: a postback is performed automatically, for example when the selected value of a dropdown changes
• callback: a method which is invoked when a certain event occurs such as clicking on a button. It also could have another meaning that a page performs a request back to the server (such as an AJAX request).

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A postback is initiated by the browser, and reloads the whole page, usually when a control on the page (e.g. a button) is changed.

With some controls (e.g. Checkboxes), you choose if changing the control should result in a postback. This property is called AutoPostback.

A callback is initiated by java script in the page, and can load/update parts of the page, e.g. by manipulating the DOM.

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Controls that support AutoPostback includes:

• List item
• ListControl
• BulletedList
• CheckBoxList
• DropDownList
• ListBox
• RadioButtonList
• CheckBox
• TextBox

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• PostBack happens when data is send to the server (he page performs a POST request to itself)
• IsPostBack helps you to identify if postback happen or not
• Autopostback if this property of control is true helps to you post as soon as data change on the contol or some event occur
• callback is a special postback, so a round-trip always occurs; however, unlike the classic postback, the script callback doesn't redraw the whole page. ViewState is not updated during a callback, it is for postback.