Set event handler on collection items after NHibernate sets its value

I've implemented an event that is fired every time a value changes in a class. I also have a class that has a collection of those items and I'd like to subscribe to those items events. I'm trying to do s开发者_运维知识库o in the setter of a property like this:

public virtual ISet<ItemType> items
{
    get
 {
  return this._items;
 }

 set
 {
  this._items = value;
  foreach (var item in this._items)
  {
   item.PropertyChanged += this.Item_ThePropertyChanged;
  }
 }
}

But I get an "illegal access to loading collection" error as soon as we reach the "in this._items" from the "for" part. Here's the stack trace:

at NHibernate.Collection.AbstractPersistentCollection.Initialize(Boolean writing)\r\n at NHibernate.Collection.AbstractPersistentCollection.Read()\r\n at NHibernate.Collection.Generic.PersistentGenericSet`1.System.Collections.Generic.IEnumerable.GetEnumerator()\r\n at MyMethod

Thanks in advance for any help

Apparently NHibernate blocks access to the collection while it is initializing the property. Does it help to change the foreach loop to a regular for loop? It may be that only the GetEnumerator() method is blocked:

for (var i = 0; i < _items.Count; i++) 
{
  _items[i].PropertyChanged += Item_ThePropertyChanged;
}