You must call the System.Windows.Forms.Control.ControlAccessibleObject.NotifyClients(AccessibleEvents) method for each System.Windows.Forms.AccessibleEvents the accessibility client applications are to be notified of. The System.Windows.Forms.Control.ControlAccessibleObject.NotifyClients(AccessibleEvents) method is typically called when a property is set or from within an event handler. For example, you might call the System.Windows.Forms.Control.ControlAccessibleObject.NotifyClients(AccessibleEvents) method and pass in an System.Windows.Forms.AccessibleEvents value of Hide from within the event handler for the Control.VisibleChanged event.