Called before shutdown if a shutdown request is received. The shutdown request can be:

- When CloseBrowser (root method) is called.

- When you press the close button in the upper right corner of the dedicated browser.

- When you select the "file" or "Exit" menu in the dedicated browser.

After the OnShutdown event is called, you can cancel the application shutdown if the AllowShutdown root property is FALSE.

For example, you can use this function to display a dialog box to confirm whether to close an application before closing it, and to close the application only when the operator gives permission. This operation is only available on the dedicated browser.