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The CheckAllCheck event fires after a user checks or unchecks the CheckAll item.To fire automatically the AutoPostBack, heckBoxes and ShowCheckAll properties should be set to True.

The event handler receives two parameters:

  1. The instance of the listbox firing the event

  2. An event arguments parameter containing the following property:

  • CheckAllChecked - shows true of false if the CheckAll checkbox is checked or unchecked
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