protected override void OnDropDownOpened(object sender, EventArgs e)

Protected Overrides Sub OnDropDownOpened(sender As Object, e As EventArgs)

Raising an event invokes the event handler through a delegate.

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