List<string> INotifyPropertyChanged event

Question

I have a simple class with a string property and a List property and I have the INofityPropertyChanged event implemented, but when I do an .Add to the string List this event is not hit so my Converter to display in the ListView is not hit. I am guessing the property changed is not hit for an Add to the List....how can I implement this in a way to get that property changed event hit???

Do I need to use some other type of collection?!

Thanks for any help!

namespace SVNQuickOpen.Configuration
{
    public class DatabaseRecord : INotifyPropertyChanged 
    {
        public DatabaseRecord()
        {
            IncludeFolders = new List<string>();
        }

        #region INotifyPropertyChanged Members

        public event PropertyChangedEventHandler PropertyChanged;

        protected void Notify(string propName)
        {
            if (this.PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propName));
            }
        }
        #endregion

        private string _name;

        public string Name
        {
            get { return _name; }

            set
            {
                this._name = value;
                Notify("Name");
            }
        }

        private List<string> _includeFolders;

        public List<string> IncludeFolders
        {
            get { return _includeFolders; }

            set
            {
                this._includeFolders = value;
                Notify("IncludeFolders");
            }
        }
    }
}

Barncard

Answer 1

You should use ObservableCollection<string> instead of List<string>, because unlike List, ObservableCollection will notify dependents when its contents are changed.

And in your case I'd make _includeFolders readonly - you can always work with one instance of the collection.

public class DatabaseRecord : INotifyPropertyChanged 
{
    private readonly ObservableCollection<string> _includeFolders;

    public ObservableCollection<string> IncludeFolders
    {
        get { return _includeFolders; }
    }

    public DatabaseRecord()
    {
        _includeFolders = new ObservableCollection<string>();
        _includeFolders.CollectionChanged += IncludeFolders_CollectionChanged;
    }

    private void IncludeFolders_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
        Notify("IncludeFolders");
    }

    ...

}

Annoy

Why should one use ObservableCollection? – Yarber

@C4u it can be used for data binding in WPF (MVVM pattern) – Annoy

Answer 2

The easiest way to make WPF's list binding work is to use a collection that implements INotifyCollectionChanged. A simple thing to do here is to replace or adapt your list with an ObservableCollection.

If you use ObservableCollection, then whenever you modify the list, it will raise the CollectionChanged event - an event that will tell the WPF binding to update. Note that if you swap out the actual collection object, you will want to raise the propertychanged event for the actual collection property.

Countercurrent

Answer 3

Your List is not going to fire the NotifyPropertyChanged event automatically for you.

WPF controls that expose an ItemsSource property are designed to be bound to an ObservableCollection<T>, which will update automatically when items are added or removed.

Seaway

Answer 4

You should have a look at ObservableCollection

Westfahl