/// <summary>
/// Converts a <see cref="CollectionNotification{T}"/> to a list of <see cref="CollectionModification{T}"/>.
/// </summary>
/// <typeparam name="T">The object that provides notification information.</typeparam>
/// <param name="notification">The <see cref="CollectionNotification{T}"/> to be converted.</param>
/// <returns>A list of <see cref="CollectionModification{T}"/> containing
/// <see cref="CollectionModificationKind.Add"/> when the specified <paramref name="notification"/> is <see cref="CollectionNotificationKind.Exists"/> or <see cref="CollectionNotificationKind.OnAdded"/>,
/// <see cref="CollectionModificationKind.Remove"/> followed by <see cref="CollectionModificationKind.Add"/> when the specified <paramref name="notification"/> is <see cref="CollectionNotificationKind.OnReplaced"/>,
/// <see cref="CollectionModificationKind.Remove"/> when the specified <paramref name="notification"/> is <see cref="CollectionNotificationKind.OnRemoved"/>, or
/// <see cref="CollectionModificationKind.Clear"/> when the specified <paramref name="notification"/> is <see cref="CollectionNotificationKind.OnCleared"/>.</returns>
public static IList <CollectionModification <T> > ToModifications <T>(this CollectionNotification <T> notification)
{
Contract.Requires(notification != null);
Contract.Ensures(Contract.Result <IList <CollectionModification <T> > >() != null);
Contract.Ensures(Contract.Result <IList <CollectionModification <T> > >().IsReadOnly);
var list = new List <CollectionModification <T> >();
switch (notification.Kind)
{
case CollectionNotificationKind.Exists:
list.Add(CollectionModification.CreateAdd <T>(notification.ExistingValues));
break;
case CollectionNotificationKind.OnAdded:
list.Add(CollectionModification.CreateAdd <T>(notification.Value));
break;
case CollectionNotificationKind.OnRemoved:
list.Add(CollectionModification.CreateRemove <T>(notification.Value));
break;
case CollectionNotificationKind.OnReplaced:
list.Add(CollectionModification.CreateRemove <T>(notification.ReplacedValue));
list.Add(CollectionModification.CreateAdd <T>(notification.Value));
break;
case CollectionNotificationKind.OnCleared:
list.Add(CollectionModification.CreateClear <T>());
break;
}
IList <CollectionModification <T> > result = list.AsReadOnly();
Contract.Assume(result.IsReadOnly);
return(result);
}
/// <summary>
/// Converts <see cref="INotifyCollectionChanged.CollectionChanged"/> events into an observable sequence of <see cref="CollectionModification{T}"/>.
/// </summary>
/// <typeparam name="T">The object that provides notification information.</typeparam>
/// <param name="source">An implementation of <see cref="INotifyCollectionChanged"/> that raises events when a collection changes.</param>
/// <remarks>
/// An <see cref="NotifyCollectionChangedAction.Add"/> event is projected into zero or more <see cref="CollectionModificationKind.Add"/> modifications.
/// A <see cref="NotifyCollectionChangedAction.Remove"/> event is projected into zero or more <see cref="CollectionModificationKind.Remove"/> modifications.
/// A <see cref="NotifyCollectionChangedAction.Move"/> event is ignored.
/// A <see cref="NotifyCollectionChangedAction.Replace"/> event is projected into zero or more sequential
/// <see cref="CollectionModificationKind.Remove"/> and <see cref="CollectionModificationKind.Add"/> modifications.
/// A <see cref="NotifyCollectionChangedAction.Reset"/> event is projected into a single <see cref="CollectionModificationKind.Clear"/> modification.
/// </remarks>
/// <returns>An observable sequence of <see cref="CollectionModification{T}"/> objects corresponding to raised events.</returns>
#else
/// <summary>
/// Converts <see cref="INotifyCollectionChanged.CollectionChanged"/> events into an observable sequence of <see cref="CollectionModification{T}"/>.
/// </summary>
/// <typeparam name="T">The object that provides notification information.</typeparam>
/// <param name="source">An implementation of <see cref="INotifyCollectionChanged"/> that raises events when a collection changes.</param>
/// <remarks>
/// An <see cref="NotifyCollectionChangedAction.Add"/> event is projected into zero or more <see cref="CollectionModificationKind.Add"/> modifications.
/// A <see cref="NotifyCollectionChangedAction.Remove"/> event is projected into zero or more <see cref="CollectionModificationKind.Remove"/> modifications.
/// A <see cref="NotifyCollectionChangedAction.Replace"/> event is projected into zero or more sequential
/// <see cref="CollectionModificationKind.Remove"/> and <see cref="CollectionModificationKind.Add"/> modifications.
/// A <see cref="NotifyCollectionChangedAction.Reset"/> event is projected into a single <see cref="CollectionModificationKind.Clear"/> modification.
/// </remarks>
/// <returns>An observable sequence of <see cref="CollectionModification{T}"/> objects corresponding to raised events.</returns>
#endif
public static IObservable <CollectionModification <T> > AsCollectionModifications <T>(this INotifyCollectionChanged source)
{
Contract.Requires(source != null);
Contract.Ensures(Contract.Result <IObservable <CollectionModification <T> > >() != null);
return(Observable.FromEventPattern <NotifyCollectionChangedEventHandler, NotifyCollectionChangedEventArgs>(
eh => source.CollectionChanged += eh,
eh => source.CollectionChanged -= eh)
.SelectMany(e =>
{
var args = e.EventArgs;
switch (args.Action)
{
case NotifyCollectionChangedAction.Add:
return Observable.Return(CollectionModification.CreateAdd(EnsureList <T>(args.NewItems)));
case NotifyCollectionChangedAction.Remove:
return Observable.Return(CollectionModification.CreateRemove(EnsureList <T>(args.OldItems)));
#if !SILVERLIGHT
case NotifyCollectionChangedAction.Move:
return Observable.Empty <CollectionModification <T> >();
#endif
case NotifyCollectionChangedAction.Replace:
return Observable.Return(CollectionModification.CreateRemove(EnsureList <T>(args.OldItems)))
.Concat(Observable.Return(CollectionModification.CreateAdd(EnsureList <T>(args.NewItems))));
case NotifyCollectionChangedAction.Reset:
return Observable.Return(CollectionModification.CreateClear <T>());
default:
throw new InvalidOperationException();
}
}));
}