By Miguel Juárez
There are several times that we would like that our collection would have the ability to notify not only when an element is added or removed from the collection itself (like the ObservableCollection does), but also to notify when any of the items’ property changes (when the items themselves are already implementing the INotifyPropertyChanged interface). Here I propose a solution for this problem.
What I’ll basically do is to extend ObservableCollection
public class NotifyCollectionChangeEventArgs : PropertyChangedEventArgs
{
public int Index { get; set; }
public NotifyCollectionChangeEventArgs(int index, string propertyName)
: base(propertyName)
{
Index = index;
}
}
public class NotifiableCollection
{
public event EventHandler<NotifyCollectionChangeEventArgs> ItemChanged;
protected override void ClearItems()
{
foreach (var item in this.Items)
{
item.PropertyChanged -= ItemPropertyChanged;
}
base.ClearItems();
}
protected override void SetItem(int index, T item)
{
this.Items[index].PropertyChanged -= ItemPropertyChanged;
base.SetItem(index, item);
this.Items[index].PropertyChanged += ItemPropertyChanged;
}
protected override void RemoveItem(int index)
{
this.Items[index].PropertyChanged -= ItemPropertyChanged;
base.RemoveItem(index);
}
protected override void InsertItem(int index, T item)
{
base.InsertItem(index, item);
item.PropertyChanged += ItemPropertyChanged;
}
private void ItemPropertyChanged(object sender, PropertyChangedEventArgs e)
{
T changedItem = sender as T;
OnItemChanged(this.IndexOf(changedItem), e.PropertyName);
}
private void OnItemChanged(int index, string propertyName)
{
if (ItemChanged != null)
{
this.ItemChanged(this, new NotifyCollectionChangeEventArgs(index, propertyName));
}
}
}
