GroupedObservableCollection

GroupedObservableCollection.cs

/// <summary>
	/// Grouped observable collection.
	/// KEY_TYPE = the type used for the group key
	/// ITEM_TYPE = the type used for the items of the list.
	/// </summary>
	public class GroupedObservableCollection<KEY_TYPE, ITEM_TYPE> : ObservableCollection<ITEM_TYPE>
	{
		/// <summary>
		/// Gets the grouping key.
		/// </summary>
		public KEY_TYPE Key
		{
			get;
			private set;
		}

		/// <summary>
		/// Initializes a new instance of the <see cref="MyContacts.GroupedObservableCollection`2"/> class.
		/// </summary>
		/// <param name="key">group key (for a list of names this could be a string representing the first character of the name)</param>
		/// <param name="groupItems">group items. These will be copied into the grouped collection</param>
		/// <param name="masterCollectionToWatch">
		/// Master collection to watch. This is optional. If provided, the master collection will be watched for changes and the
		/// grouped collection will update itself according to these changes.
		/// Note: GroupedObservableCollection will subscribe to the CollectionChanged event of the master collection. 
		/// </param>
		public GroupedObservableCollection(KEY_TYPE key, IEnumerable<ITEM_TYPE> groupItems, INotifyCollectionChanged masterCollectionToWatch = null)
		{
			this.Key = key;

			// Copy all the group items over.
			foreach (var item in groupItems)
			{
				this.Items.Add (item);
			}

			// Watch the master if it is set. Whenever something changes, we also update ourselves.
			if (masterCollectionToWatch != null)
			{
				masterCollectionToWatch.CollectionChanged += HandleMasterCollectionChanged;
			}
		}

		void HandleMasterCollectionChanged (object sender, NotifyCollectionChangedEventArgs e)
		{
			switch(e.Action)
			{
				case NotifyCollectionChangedAction.Remove:
					// Remove old items from our group.
					foreach (ITEM_TYPE item in e.OldItems)
					{
						Debug.WriteLine ("GroupedObservableCollection removing [{0}]", item);
						this.Remove(item);
					}
					break;

				case NotifyCollectionChangedAction.Add:
					// Add items to our group.
					foreach (ITEM_TYPE item in e.NewItems)
					{
						Debug.WriteLine ("GroupedObservableCollection adding [{0}]", item);
						this.Add(item);
					}
					break;

				case NotifyCollectionChangedAction.Replace:
					// TODO: Implement. Need to check what is in the event props.

					// Replace items.
					foreach (ITEM_TYPE item in e.OldItems)
					{
						Debug.WriteLine ("GroupedObservableCollection replacing old item [{0}]", item);
					}

					// Replace items.
					foreach (ITEM_TYPE item in e.NewItems)
					{
						Debug.WriteLine ("GroupedObservableCollection replacing new item [{0}]", item);
					}
					Debug.WriteLine ("-----");

					break;

				case NotifyCollectionChangedAction.Move:
					// TODO: Implement. Need to check what is in the event props.

					// Move items.
					foreach (ITEM_TYPE item in e.OldItems)
					{
						Debug.WriteLine ("GroupedObservableCollection moving old item [{0}]", item);
					}

					// Move items.
					foreach (ITEM_TYPE item in e.NewItems)
					{
						Debug.WriteLine ("GroupedObservableCollection moving new item [{0}]", item);
					}
					Debug.WriteLine ("-----");

					break;

				case NotifyCollectionChangedAction.Reset:
					Debug.WriteLine ("GroupedObservableCollection clearing content");
					this.Clear ();
					break;
			}
		}
	}