This is loosely modelled after the standard PropertyChangeEvent objects.

For an object to correctly fire these events, they must follow a broad outline like this:

CopyC#

public void mutator(foo arg) throw ChangeVetoException {
  ChangeEvent cevt = new ChangeEvent(this, SOME_EVENT_TYPE, arg);
  synchronized(changeSupport) {
    changeSupport.firePreChangeEvent(cevt);
    // update our state using arg
    // ...
    changeSupport.firePostChangeEvent(cevt);
  }
}

The methods that delegate adding and removing listeners to a ChangeSupport must take responsibility for synchronizing on the delegate.

Original BioJava version by Matthew Pocock, Thomas Down, Keith James (docs), and Kalle Naslund (tiny bugfix). Port to C# by Doug Swisher.