/// <summary>
/// Binds a <see cref="NotifyCollectionChangedEventHandler"/> to all collections by the name <paramref name="collectionPropertyName"/> on the elements of type <typeparamref name="T"/> on the specified collection.
/// Note: not all elements of <paramref name="collection"/> are considered; only those of type <typeparamref name="T"/>. You could specify <see cref="INotifyPropertyChanged"/> to revert this.
/// </summary>
/// <returns> a disposble which unhooks the <paramref name="handler"/> from all elements. </returns>
public static IDisposable BindElements <TCollection, T>(
this TCollection collection,
string collectionPropertyName,
NotifyCollectionChangedEventHandler handler) where T : INotifyPropertyChanged where TCollection : INotifyCollectionChanged, IEnumerable <object>
{
Contract.Requires(collection != null);
Contract.Requires(handler != null);
PropertyChangedEventHandler intermediate = (element, e) =>
{
if (e.PropertyName == collectionPropertyName)
{
var _e = (IPropertyMutatedEventArgs)e;
if (_e.OldValue is INotifyCollectionChanged oldCollection)
{
oldCollection.CollectionChanged -= handler;
}
if (_e.NewValue is INotifyCollectionChanged newCollection)
{
newCollection.CollectionChanged += handler;
}
}
};
var collectionHandler = CollectionChangedEventHandler <object> .Create <TCollection>(add : add, remove : remove);
collection.CollectionChanged += collectionHandler.CollectionChanged;
return(new Disposable(() =>
{
collection.CollectionChanged -= collectionHandler.CollectionChanged;
foreach (T element in collection)
{
element.PropertyChanged -= intermediate;
}
}));
void add(TCollection sender, IReadOnlyList <object> newElements, int index)
{
Contract.Assert(ReferenceEquals(collection, sender));
foreach (T element in newElements.OfType <T>())
{
element.PropertyChanged += intermediate;
intermediate(element, PropertyMutatedEventArgsExtensions.From(element, collectionPropertyName));
}
}
void remove(TCollection sender, IReadOnlyList <object> oldElements, int index)
{
Contract.Assert(ReferenceEquals(collection, sender));
foreach (T element in oldElements.OfType <T>())
{
element.PropertyChanged -= intermediate;
}
}
}
/// <summary>
/// Binds a <see cref="PropertyChangedEventHandler"/> to all elements on the specified collection.
/// </summary>
/// <returns> a disposble which unhooks the <paramref name="handler"/> from all elements. </returns>
public static IDisposable BindElements <TCollection, T>(this TCollection collection, PropertyChangedEventHandler handler) where T : INotifyPropertyChanged where TCollection : INotifyCollectionChanged, IEnumerable <T>
{
Contract.Requires(collection != null);
Contract.Requires(handler != null);
var collectionHandler = CollectionChangedEventHandler <T> .Create <TCollection>(add : add, remove : remove);
collection.CollectionChanged += collectionHandler.CollectionChanged;
return(new Disposable(() =>
{
collection.CollectionChanged -= collectionHandler.CollectionChanged;
foreach (T element in collection)
{
element.PropertyChanged -= handler;
}
}));
void add(TCollection sender, IReadOnlyList <T> newElements, int index)
{
Contract.Assert(ReferenceEquals(collection, sender));
foreach (T element in newElements)
{
element.PropertyChanged += handler;
}
}
void remove(TCollection sender, IReadOnlyList <T> oldElements, int index)
{
Contract.Assert(ReferenceEquals(collection, sender));
foreach (T element in oldElements)
{
element.PropertyChanged -= handler;
}
}
}
