ObservableQueue?

Question

Has anyone written a version of .Net\'s generic Queue that implements INotifyCollectionChanged, or is there one hidden deep in the .Net framework somewhere already?

Answer 1

A quick search didn't show any results. But the interface is simple and it would be almost trivial to extend the Queue class and add support for the interface. Just override all methods thusly:

// this isn't the best code ever; refactor as desired
protected void OnCollectionChanged( NotifyCollectionChangedEventArgs ccea){
  var temp = CollectionChanged;
  if(temp != null) temp(this, ccea);  
}

// and later in the class

public override SomeMethodThatAltersTheQueue(object something){
  // record state of collection prior to change
  base.SomeMethodThatAltersTheQueue(something)
  // create NotifyCollectionChangedEventArgs with prior state and new state
  OnCollectionChanged(ccea);
}

Answer 2

I used the same approach as Chris Wenham. Under load, performance suffers because new NotifyCollectionChangedEventArgs need to be allocated for each Enqueue/Dequeue.

Regardless, in the Enqueue, send args with NotifyCollectionChangedAction.Add, the item added, and Count-1 as the index. In the Dequeue, send args with NotifyCollectionChangedAction.Remove, the item removed, and index 0.