Notification of Collection Update for IDataErrorInfo Validation

Question

I would like to notify the binding system in WPF of a change in a collection's item so that a validation through IDataErrorInfo gets reevaluated whenever an item inside a collection changes. I have a custom list type which implements INotifyCollectionChanged (and works properly). But somehow the validation logic is never called, because (or at least I am assuming) that this notification does not reach the right place. Is this scenario even possible? What have I missed?

[Edit]

So basically the "architecture" is the following:

MVVM base class implements IDataErrorInfo and you can register DataValidators with lambdas in the derived MVVM classes, such as:

RegisterDataValidator(() => People, () => (People.Count == 0) ? "At least one person must be specified" : null);

The indexer on the base class checks the registered validator and returns the returned by it.

I have a SmartBindingList<T> where T: INotifyPropertyChange which is basically a list that when items are added to it, registers the items' PropertyChangedEvent and reacts to these events by firing the CollectionChanged event on the class itself:

private void OnSubPropertyChanged (object sender, PropertyChangedEventArgs e)
    {
        if (sender is T1)
        {
            if (CollectionChanged != null)
            {
                NotifyCollectionChangedEventArgs eventArgs = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Replace, sender, sender);
                CollectionChanged(this, eventArgs);
            }
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(myPropertyName));
            }
        }
    }

So all this works nicely, but when the code runs on the CollectionChanged(this, eventArgs) line, nothing happens in terms of validation. It should be wired up correctly, because when I add something to the collection, it works perfectly. What am I missing?

Phil Phil · Accepted Answer · 2012-03-12T19:31:25

This is a bit of stab in the dark without some example code, but try raising your OnPropertyChanged notification for the properties that have changed. This should cause validation to be re-evaluated.

Notification of Collection Update for IDataErrorInfo Validation

1 Answers