Property Changed from ObservableCollectio<T> to Main class - wpf

Question

I think this is a stupid problem but...
I have a Window class with a Treeview bind to a Observablecollection<T> foo; T is my class (in another file .cs).
My Observablecollection foo have OnPropertyChanged for add/delete element and works ok.
The problem is for my class T: it has 5 properties and one have OnPropertyChanged: when I programmatically change an element of my class T I have OnPropertyChanged in class T (obviously) but... how can I know it from Window class for do something?

Answer 1

You want to be able to listen to propertychange events on the items inside the observable collection?
To do this, I created an extension to ObsercableCollection that bubbles up these events to a collection level, so I can subscribe to collection.CollectionChanged (adding and removing items) and collection.ItemInCollectionChange (property of an item inside the collection has changed):
//public class ItemInCollectionChangeEventArgs
public class ItemInCollectionChangeEventArgs : EventArgs
{
public object Item { get; internal set; }
public PropertyChangedEventArgs PropertyChangedEventArgs { get; internal set; }
}
public delegate void ItemInCollectionChangeEventHandler(Object sender, ItemInCollectionChangeEventArgs e);
//TODO Make this throw a separate event for refreshing
public class ItemsChangeObservableCollection<T> :
ObservableCollection<T> where T : INotifyPropertyChanged
{
public event ItemInCollectionChangeEventHandler ItemInCollectionChangeEvent;
public ItemsChangeObservableCollection() : base()
{
}
public ItemsChangeObservableCollection(IEnumerable<T> collection) : base()
{
foreach (T item in collection)
{
Add(item);
}
}
protected virtual void OnItemInCollectionChange(ItemInCollectionChangeEventArgs e)
{
ItemInCollectionChangeEventHandler handler = ItemInCollectionChangeEvent;
if (handler != null)
{
handler(this, e);
}
}
protected override void OnCollectionChanged(NotifyCollectionChangedEventArgs e)
{
if (e.Action == NotifyCollectionChangedAction.Add)
{
RegisterPropertyChanged(e.NewItems);
}
else if (e.Action == NotifyCollectionChangedAction.Remove)
{
UnRegisterPropertyChanged(e.OldItems);
}
else if (e.Action == NotifyCollectionChangedAction.Replace)
{
UnRegisterPropertyChanged(e.OldItems);
RegisterPropertyChanged(e.NewItems);
}
base.OnCollectionChanged(e);
}
protected override void ClearItems()
{
UnRegisterPropertyChanged(this);
base.ClearItems();
}
private void RegisterPropertyChanged(IList items)
{
foreach (INotifyPropertyChanged item in items)
{
if (item != null)
{
item.PropertyChanged += new PropertyChangedEventHandler(item_PropertyChanged);
}
}
}
private void UnRegisterPropertyChanged(IList items)
{
foreach (INotifyPropertyChanged item in items)
{
if (item != null)
{
item.PropertyChanged -= new PropertyChangedEventHandler(item_PropertyChanged);
}
}
}
private void item_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
OnItemInCollectionChange(new ItemInCollectionChangeEventArgs { Item = sender, PropertyChangedEventArgs = e });
//base.OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
}
}