Items control data source's item property update, not reflecfted in the items control's itempanel template instance

I have a custom panel control that is intended to be used as an itemspaneltemplate in a items control.

The itemscontrol will be databound to a data source.

This开发者_运维技巧 datasource is a List, and each item in the list is a custom business object. In the application, the user is able to update each of these business objects in the list, and that fires the notification on property changed as expected.

Now my problem is here:

When the user updates the object's properties in the data source (the itms in the List) that the items control is bound to, my custom panel control is not able to get that notification, so as a result the items control does not get updated with the updated items in its view.

I tried using an ObservableCollection instead of List - the problem is still the same.

I must be missing something fundamental here... please help with any pointers, answers or solution.

Change notification in a collection is a bit tricky. Say you have a collection of Products. you can implement change notification is three different places.

1. Change notification in the Product class (implementing INotifyPropertyChanged in class Product)
2. Change notification in the collection itself (i.e. using ObservableCollection)
3. Change notification in the class that holds the collection, that is, implementing INotifyPropertyChanged on the class that contains the collection. (usually this would be the ViewModel under MVVM)

Those tree ways are not the same, and each is for a different situation.

Let's say that the collection is ObservableCollection<Product> Products {get;set;} if you want changes in the product to register (i.e., if you're doing something like Products[0].Name = "New Product"; then #1 is the right one.

If you want to do Products.Add(new Product(...)) then #2 is the right one.

If you want to do Products = new ObservableCollection<Product>() then #3 is the correct one. This is especially tricky since i'm not changing the collection, but creating a new one, so the ObservableCollection won't help - I'd need to implement INPC in the containing class.