protected override void OnShapeChanged(ShapeEventArgs e)
{
// Do any rectangle-specific processing here.
// Call the base class event invocation method.
base.OnShapeChanged(e);
}
private void HandleShapeChanged(object sender, ShapeEventArgs e)
{
Shape s = (Shape)sender;
// Diagnostic message for demonstration purposes.
Console.WriteLine("Received event. Shape area is now {0}", e.NewArea);
// Redraw the shape here.
s.Draw();
}
//The event-invoking method that derived classes can override.
protected virtual void OnShapeChanged(ShapeEventArgs e)
{
// Make a temporary copy of the event to avoid possibility of
// a race condition if the last subscriber unsubscribes
// immediately after the null check and before the event is raised.
EventHandler <ShapeEventArgs> handler = ShapeChanged;
if (handler != null)
{
handler(this, e);
}
}