Classes

The TNotifyEvent type is the type for events that have no event-specific parameters. These events simply notify the component that a specific event occurred. For example, OnClick, which is of type TNotifyEvent, notifies the control that a click event occurred on the control.  

The Sender parameter is the object whose event handler is called. For example, with the OnClick event of a button, the Sender parameter is the button component that is clicked.