You should use INotifyPropertyChanged when you really change a property - if it's a value type when you change its value and if it's a reference type(like List) when you change the reference. Lets say you have a List Foo, when you add an item to Foo you don't change it - it's still Foo and it have the same reference as before so the INotifyPropertyChanged won't work. When you change collections your collection should implement the INotifyCollectionChanged interface and the List does not.
I'll advise you to change your GraphList from List<IChart> to ObservableCollection<IChart> or if don't want to use ObservableCollection you should create your own collection which implements the INotifyCollectionChanged and whenever you change its items you should fire the NotifyCollectionChanged().
If you need further assistance feel free to ask.
All the best,
the Telerik team
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