The event handler method receives the following arguments:
sender
An ObservableCollection instance, which is the source of the event. This object will be passed to the handler function as the first argument.
args
A NotifyCollectionChangingEventArgs instance, which contains event data. This object will be passed to the handler function as the second argument.

The cancel property of NotifyCollectionChangingEventArgs allows you to stop the action.

The following code handles the collectionChanging event on the items collection of a ListView object that is of type ObservableCollection:

JavaScript  Copy Code
var nodeList = new ui.ListView(document.getElementById("nodeList")); nodeList.items.collectionChanging.addEventListener(itemsCollectionChangingEventHandler); function itemsCollectionChangingEventHandler(sender, args) {  if(args.action == ui.NotifyCollectionChangedAction.Add)  {      //do something  }  }

ObservableCollection Members
ObservableCollection Class
MindFusion.Common.Collections Namespace