CODEWITHSUNDEEP
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Johannes Schacht
Johannes Schacht

Reputation: 1354

Can't use PropertyChanged from ObservableCollection

I'm puzzled. I try using the PropertyChanged event from an ObservableCollection, but the compiler does not know the event. CollectionChanged he knows. MSDN says the ObservableCollection has the event (https://msdn.microsoft.com/en-us/library/ms653376.aspx). What am I doing wrong?

ObservableCollection<int> xx = new ObservableCollection<int>();
xx.PropertyChanged += (s, a) => { };

Upvotes: 3

Views: 1717

Answers (1)

walther
walther

Reputation: 13600

PropertyChanged is a protected event, that's why it's not accessible from your code. As you surely know, protected means it's accessible only from itself and from derived classes.

When it comes to ObservableCollection, we have an event CollectionChanged to know, when the collection changes (an item got deleted or added). If we need to know, if the item of the collection has been changed, you need to use a custom implementation, for example from here: TrulyObservableCollection

Also, as @O. R. Mapper correctly pointed out, there's is a way of doing this without creating a derived type. As ObservableCollection implements INotifyPropertyChanged explicitly, you have to cast the instance to the interface and then you can access properties, events and methods of the interface. So something like this works as well (but it's ugly to be honest):

ObservableCollection<int> xx = new ObservableCollection<int>();
((INotifyPropertyChanged)xx).PropertyChanged += (s, a) => { };

Upvotes: 5

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