protected virtual void OnKeyDown(object sender, KeyEventArgs e)

Protected Overridable Sub OnKeyDown(sender As Object, e As KeyEventArgs)

Raising an event invokes the event handler through a delegate.

The OnKeyDown method also allows derived classes to handle the event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

Notes to Inheritors:

When overriding OnKeyDown in a derived class, be sure to call the base class's OnKeyDown method so that registered delegates receive the event.