M→VM 用コレクションラッパ

ObservableCollectionWrapper.cs

// usage:
// 
// Model のコレクションの変化を自動的に反映する ViewModel コレクションを作成
// ObservableCollectionWrapper.Create(modelCollection, (Model m) => new ViewModel(m))
// 
// 任意の ViewModel 側コレクションを Model コレクションに同期させる
// ViewModel コレクションへの操作を Model 側に反映させることもできる (Caliburn.Micro での Conductor の Items に使用するなど)
// ObservableCollectionWrapper.Create(modelCollection, viewModelCollection, (Model m) => new ViewModel(m), vm => vm.Model)
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;

namespace Linearstar.Coah
{
	public class ObservableCollectionWrapper<TInputCollection, TInput, TOutputCollection, TOutput> : IReadOnlyList<TOutput>, INotifyCollectionChanged, IDisposable
		where TInputCollection : IList<TInput>, INotifyCollectionChanged
		where TOutputCollection : IList<TOutput>, INotifyCollectionChanged
	{
		readonly Func<TInput, TOutput> converter;
		readonly Func<TOutput, TInput> reverseSelector;
		bool isUpdating;

		public TInputCollection InputCollection { get; }
		public TOutputCollection OutputCollection { get; }

		public event NotifyCollectionChangedEventHandler CollectionChanged
		{
			add
			{
				this.OutputCollection.CollectionChanged += value;
			}
			remove
			{
				this.OutputCollection.CollectionChanged -= value;
			}
		}

		public TOutput this[int index] => this.OutputCollection[index];
		public int Count => this.OutputCollection.Count;

		public ObservableCollectionWrapper(TInputCollection inputCollection, TOutputCollection outputCollection, Func<TInput, TOutput> converter)
		{
			this.InputCollection = inputCollection;
			this.OutputCollection = outputCollection;
			this.converter = converter;

			foreach (var i in this.InputCollection)
				this.OutputCollection.Add(converter(i));

			inputCollection.CollectionChanged += InputCollection_CollectionChanged;
		}

		public ObservableCollectionWrapper(TInputCollection inputCollection, TOutputCollection outputCollection, Func<TInput, TOutput> converter, Func<TOutput, TInput> reverseSelector)
			: this(inputCollection, outputCollection, converter)
		{
			this.reverseSelector = reverseSelector;
			outputCollection.CollectionChanged += OutputCollection_CollectionChanged;
		}

		void InputCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
		{
			if (isUpdating)
				return;

			isUpdating = true;

			switch (e.Action)
			{
				case NotifyCollectionChangedAction.Add:
					foreach (TInput i in e.NewItems)
						this.OutputCollection.Add(converter(i));

					break;
				case NotifyCollectionChangedAction.Move:
					var item = this.OutputCollection[e.OldStartingIndex];

					this.OutputCollection.RemoveAt(e.OldStartingIndex);
					this.OutputCollection.Insert(e.NewStartingIndex - (e.NewStartingIndex > e.OldStartingIndex ? 1 : 0), item);

					break;
				case NotifyCollectionChangedAction.Remove:
					for (var i = e.OldItems.Count - 1; i >= 0; i--)
						this.OutputCollection.RemoveAt(e.OldStartingIndex + i);

					break;
				case NotifyCollectionChangedAction.Replace:
					for (int i = 0; i < e.OldItems.Count; i++)
						this.OutputCollection[i + e.OldStartingIndex] = converter((TInput)e.NewItems[i]);

					break;
				case NotifyCollectionChangedAction.Reset:
					this.OutputCollection.Clear();

					foreach (var i in this.InputCollection)
						this.OutputCollection.Add(converter(i));

					break;
			}

			isUpdating = false;
		}

		void OutputCollection_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
		{
			if (isUpdating)
				return;

			isUpdating = true;

			switch (e.Action)
			{
				case NotifyCollectionChangedAction.Add:
					foreach (TOutput i in e.NewItems)
						this.InputCollection.Add(reverseSelector(i));

					break;
				case NotifyCollectionChangedAction.Move:
					var item = this.InputCollection[e.OldStartingIndex];

					this.InputCollection.RemoveAt(e.OldStartingIndex);
					this.InputCollection.Insert(e.NewStartingIndex - (e.NewStartingIndex > e.OldStartingIndex ? 1 : 0), item);

					break;
				case NotifyCollectionChangedAction.Remove:
					for (var i = e.OldItems.Count - 1; i >= 0; i--)
						this.InputCollection.RemoveAt(e.OldStartingIndex + i);

					break;
				case NotifyCollectionChangedAction.Replace:
					for (int i = 0; i < e.OldItems.Count; i++)
						this.InputCollection[i + e.OldStartingIndex] = reverseSelector((TOutput)e.NewItems[i]);

					break;
				case NotifyCollectionChangedAction.Reset:
					this.InputCollection.Clear();

					foreach (var i in this.OutputCollection)
						this.InputCollection.Add(reverseSelector(i));

					break;
			}

			isUpdating = false;
		}

		public IEnumerator<TOutput> GetEnumerator() => this.OutputCollection.GetEnumerator();
		IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();

		public void Dispose()
		{
			this.InputCollection.CollectionChanged -= InputCollection_CollectionChanged;
			this.OutputCollection.CollectionChanged -= OutputCollection_CollectionChanged;
		}
	}

	public static class ObservableCollectionWrapper
	{
		public static ObservableCollectionWrapper<TCollection, TInput, ObservableCollection<TOutput>, TOutput> Create<TCollection, TInput, TOutput>(TCollection collection, Func<TInput, TOutput> converter)
			where TCollection : IList<TInput>, INotifyCollectionChanged =>
			new ObservableCollectionWrapper<TCollection, TInput, ObservableCollection<TOutput>, TOutput>(collection, new ObservableCollection<TOutput>(), converter);

		public static ObservableCollectionWrapper<TInputCollection, TInput, TOutputCollection, TOutput> Create<TInputCollection, TInput, TOutputCollection, TOutput>(TInputCollection inputCollection, TOutputCollection outputCollection, Func<TInput, TOutput> converter, Func<TOutput, TInput> reverseSelector)
			where TInputCollection : IList<TInput>, INotifyCollectionChanged
			where TOutputCollection : IList<TOutput>, INotifyCollectionChanged =>
			new ObservableCollectionWrapper<TInputCollection, TInput, TOutputCollection, TOutput>(inputCollection, outputCollection, converter, reverseSelector);
	}
}