true, to perform a postback when the Action is executed; false, to perform a callback.
Set the IsPostBackRequired property to true for Actions that should be executed on postback. For instance, the built-in Export Action is executed on postback, because a postback is required to transmit a file to the client. An example of using this property is provided in the How to: Print a Report Without Displaying a Preview topic.
Set this property to true when implementing a custom Action that initiates a file download in a web application.