RecyclableList.Enumerator performance improvements to match List<T>'s performance. Dirty state.

Recyclable.Collections.Benchmarks/Benchmarks/ForEach.cs

@@ -0,0 +1,45 @@
+namespace Recyclable.Collections.Benchmarks
+{
+	public partial class RecyclableCollectionsBenchmarks
+	{
+		public void Array_ForEach()
+		{
+			foreach (var item in TestObjects)
+			{
+				DoNothing(item);
+			}
+		}
+
+		public void List_ForEach()
+		{
+			foreach (var item in TestObjectsAsList)
+			{
+				DoNothing(item);
+			}
+		}
+
+		public void PooledList_ForEach()
+		{
+			foreach (var item in TestObjectsAsPooledList)
+			{
+				DoNothing(item);
+			}
+		}
+
+		public void RecyclableList_ForEach()
+		{
+			foreach (var item in TestObjectsAsRecyclableList)
+			{
+				DoNothing(item);
+			}
+		}
+
+		public void RecyclableLongList_ForEach()
+		{
+			foreach (var item in TestObjectsAsRecyclableLongList)
+			{
+				DoNothing(item);
+			}
+		}
+	}
+}

Recyclable.Collections.Benchmarks/Benchmarks/RecyclableCollections.Benchmarks.cs

@@ -5,9 +5,9 @@ namespace Recyclable.Collections.Benchmarks
 {
 	public enum RecyclableCollectionsBenchmarkType
 	{
-		Add_WithCapacity, Add, AddRange_WithCapacity, AddRangeWhenSourceIsArray, AddRangeWhenSourceIsIEnumerable,
+		Unknown, Add_WithCapacity, Add, AddRange_WithCapacity, AddRangeWhenSourceIsArray, AddRangeWhenSourceIsIEnumerable,
 		AddRangeWhenSourceIsIList, AddRangeWhenSourceIsList, AddRangeWhenSourceIsSameType, Contains_FirstItems,
-		Contains_LastItems, Count, Create_WithCapacity, Create, GetItem, IndexOf_BestAndWorstCases, IndexOf_FirstItems,
+		Contains_LastItems, Count, Create_WithCapacity, Create, ForEach, GetItem, IndexOf_BestAndWorstCases, IndexOf_FirstItems,
 		IndexOf_LastItems, LongCount, Remove_FirstItems, Remove_LastItems, RemoveAt_FirstItems, RemoveAt_LastItems,
 		SetItem,
 	}
@@ -17,52 +17,53 @@ namespace Recyclable.Collections.Benchmarks
 		public RecyclableCollectionsBenchmarks() : base()
 		{
 			TestObjectCount = 1;
-			BaseDataType = RecyclableCollectionsBenchmarkSource.List;
-			DataType = RecyclableCollectionsBenchmarkSource.RecyclableLongList;
+			//BaseDataType = RecyclableCollectionsBenchmarkSource.List;
+			DataType = RecyclableCollectionsBenchmarkSource.RecyclableList;
 		}
 
 		[Params
 		(
-			RecyclableCollectionsBenchmarkType.Add_WithCapacity,
-			RecyclableCollectionsBenchmarkType.Add,
-			RecyclableCollectionsBenchmarkType.AddRange_WithCapacity,
-			RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsArray,
-			RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsIEnumerable,
-			RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsIList,
-			RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsList,
-			RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsSameType,
-			RecyclableCollectionsBenchmarkType.Contains_FirstItems,
-			RecyclableCollectionsBenchmarkType.Contains_LastItems,
-			RecyclableCollectionsBenchmarkType.Count,
-			RecyclableCollectionsBenchmarkType.Create_WithCapacity,
-			RecyclableCollectionsBenchmarkType.Create,
-			RecyclableCollectionsBenchmarkType.GetItem,
-			RecyclableCollectionsBenchmarkType.IndexOf_BestAndWorstCases,
-			RecyclableCollectionsBenchmarkType.IndexOf_FirstItems,
-			RecyclableCollectionsBenchmarkType.IndexOf_LastItems,
-			RecyclableCollectionsBenchmarkType.LongCount,
-			RecyclableCollectionsBenchmarkType.Remove_FirstItems,
-			RecyclableCollectionsBenchmarkType.Remove_LastItems,
-			RecyclableCollectionsBenchmarkType.RemoveAt_FirstItems,
-			RecyclableCollectionsBenchmarkType.RemoveAt_LastItems,
-			RecyclableCollectionsBenchmarkType.SetItem
+			//RecyclableCollectionsBenchmarkType.Add_WithCapacity,
+			//RecyclableCollectionsBenchmarkType.Add,
+			//RecyclableCollectionsBenchmarkType.AddRange_WithCapacity,
+			//RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsArray,
+			//RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsIEnumerable,
+			//RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsIList,
+			//RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsList,
+			//RecyclableCollectionsBenchmarkType.AddRangeWhenSourceIsSameType,
+			//RecyclableCollectionsBenchmarkType.Contains_FirstItems,
+			//RecyclableCollectionsBenchmarkType.Contains_LastItems,
+			//RecyclableCollectionsBenchmarkType.Count,
+			//RecyclableCollectionsBenchmarkType.Create_WithCapacity,
+			//RecyclableCollectionsBenchmarkType.Create,
+			RecyclableCollectionsBenchmarkType.ForEach
+			//RecyclableCollectionsBenchmarkType.GetItem,
+			//RecyclableCollectionsBenchmarkType.IndexOf_BestAndWorstCases,
+			//RecyclableCollectionsBenchmarkType.IndexOf_FirstItems,
+			//RecyclableCollectionsBenchmarkType.IndexOf_LastItems,
+			//RecyclableCollectionsBenchmarkType.LongCount,
+			//RecyclableCollectionsBenchmarkType.Remove_FirstItems,
+			//RecyclableCollectionsBenchmarkType.Remove_LastItems,
+			//RecyclableCollectionsBenchmarkType.RemoveAt_FirstItems,
+			//RecyclableCollectionsBenchmarkType.RemoveAt_LastItems,
+			//RecyclableCollectionsBenchmarkType.SetItem
 		)]
 
 		public RecyclableCollectionsBenchmarkType TestCase { get; set; } = RecyclableCollectionsBenchmarkType.IndexOf_BestAndWorstCases;
 
-		[Params
-		(
-			RecyclableCollectionsBenchmarkSource.List
-		)]
+		//[Params
+		//(
+		//	RecyclableCollectionsBenchmarkSource.List
+		//)]
 		public override RecyclableCollectionsBenchmarkSource BaseDataType { get => base.BaseDataType; set => base.BaseDataType = value; }
 
 		[Params
 		(
-			RecyclableCollectionsBenchmarkSource.Array,
-			RecyclableCollectionsBenchmarkSource.List,
-			RecyclableCollectionsBenchmarkSource.PooledList,
-			RecyclableCollectionsBenchmarkSource.RecyclableList,
-			RecyclableCollectionsBenchmarkSource.RecyclableLongList
+			//RecyclableCollectionsBenchmarkSource.Array,
+			//RecyclableCollectionsBenchmarkSource.List,
+			//RecyclableCollectionsBenchmarkSource.PooledList,
+			RecyclableCollectionsBenchmarkSource.RecyclableList
+			//RecyclableCollectionsBenchmarkSource.RecyclableLongList
 		)]
 		public override RecyclableCollectionsBenchmarkSource DataType { get => base.DataType; set => base.DataType = value; }
 

Recyclable.Collections.Benchmarks/POC/PocBenchmarkBase.cs

@@ -50,7 +50,7 @@ namespace Recyclable.Collections.Benchmarks.POC
 		// [Params(1, 10, 1024, 10240, RecyclableDefaults.MinPooledArrayLength, RecyclableDefaults.MinItemsCountForParallelization)]
 		// [Params(RecyclableDefaults.MinItemsCountForParallelization * 3)]
 		// [Params(1_048_576)]
-		public virtual int TestObjectCount { get; set; } = 1; //33_554_432; //524_288; //131_072;
+		public virtual int TestObjectCount { get; set; } = 131_072; //1; //33_554_432; //524_288; //131_072;
 		public virtual int TestObjectCountForSlowMethods => (TestObjectCount / 2) + 1;// Math.Min(TestObjectCount, 131_072);
 
 		// [Params(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200)]

Recyclable.Collections.Benchmarks/Program.cs

@@ -23,17 +23,16 @@ public static class Program
 		// ****************
 		// *** Template ***
 		// ****************
-		//var benchmark = new RecyclableCollectionsBenchmarks();
-		//benchmark.Setup();
+		var benchmark = new RecyclableCollectionsBenchmarks();
+		benchmark.Setup();
 
 		//foreach (var _ in Enumerable.Range(1, 1000))
 		//{
-			// benchmark.RecyclableLongList_Remove_FirstItems();
-			// benchmark.RecyclableLongList_RemoveAt_LastItems();
-			// benchmark.List_RemoveAt_LastItems();
+		benchmark.List_ForEach();
+		benchmark.RecyclableList_ForEach();
 		//}
 
-		//benchmark.Cleanup();
+		benchmark.Cleanup();
 	}
 
 	static void RunPocBenchmarks()
@@ -53,8 +52,8 @@ public static class Program
 	static void Main(string[] args)
 	{
 		RunRecyclableCollectionsBenchmarks();
-		// RunPocBenchmarks();
-		// RunSelectedBenchmarks();
-		// RunAssemblyBenchmarks();
+		//RunPocBenchmarks();
+		//RunSelectedBenchmarks();
+		//RunAssemblyBenchmarks();
 	}
 }

Recyclable.Collections/Pools/RecyclableCollectionVersionPool.cs

@@ -1,20 +1,15 @@
 using Microsoft.Extensions.ObjectPool;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 
 namespace Recyclable.Collections.Pools
 {
-	public class RecyclableCollectionVersionPool
-	{
-		private static readonly RecyclableCollectionVersionPool _shared = new();
-		public static RecyclableCollectionVersionPool Shared => _shared;
+	//public class RecyclableCollectionVersionPool
+	//{
+	//	private static readonly RecyclableCollectionVersionPool _shared = new();
+	//	public static RecyclableCollectionVersionPool Shared => _shared;
 
-		private ObjectPool<RecyclableCollectionVersion> _pool = new DefaultObjectPool<RecyclableCollectionVersion>(new DefaultPooledObjectPolicy<RecyclableCollectionVersion>());
+	//	private readonly ObjectPool<RecyclableCollectionVersion> _pool = new DefaultObjectPool<RecyclableCollectionVersion>(new DefaultPooledObjectPolicy<RecyclableCollectionVersion>());
 
-		public RecyclableCollectionVersion Get() => _pool.Get().Reset();
-		public void Return(RecyclableCollectionVersion version) => _pool.Return(version);
-	}
+	//	public RecyclableCollectionVersion Get() => _pool.Get().Reset();
+	//	public void Return(RecyclableCollectionVersion version) => _pool.Return(version);
+	//}
 }

Recyclable.Collections/Pools/RecyclableList.EnumeratorPool.cs

@@ -0,0 +1,19 @@
+using Microsoft.Extensions.ObjectPool;
+
+namespace Recyclable.Collections
+{
+	public partial class RecyclableList<T>
+	{
+		//internal class RecyclableListEnumeratorPool
+		//{
+		//	private static readonly RecyclableListEnumeratorPool _shared = new();
+		//	public static RecyclableListEnumeratorPool Shared => _shared;
+
+		//	private readonly ObjectPool<RecyclableListEnumerator> _pool = new DefaultObjectPool<RecyclableListEnumerator>(new DefaultPooledObjectPolicy<RecyclableListEnumerator>());
+
+		//	public RecyclableListEnumerator Get(RecyclableList<T> list) => _pool.Get().Reset(this, list);
+
+		//	public void Return(RecyclableListEnumerator version) => _pool.Return(version);
+		//}
+	}
+}

Recyclable.Collections/RecyclableCollectionVersion.cs

@@ -2,39 +2,88 @@
 
 namespace Recyclable.Collections
 {
+	public delegate void VersionChangedEventHandler();
+
 	public sealed class RecyclableCollectionVersion
 	{
-		private ulong _enumeratorCount;
-		public ulong Version;
+		//private ulong _enumeratorCount;
+
+		//private ulong _version;
+		//public ulong Version
+		//{
+		//	get => _version;
+			
+		//	set
+		//	{
+		//		_version = value;
+		//		_versionChanged?.Invoke(this, EventArgs.Empty);
+		//	}
+		//}
+
+		//public uint Version { get; set; }
+
 		public bool IsVersioned;
 
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public void Inc() => _ = unchecked(Version++);
-
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public void AddEnumerator()
+		private VersionChangedEventHandler? _versionChanged;
+		public event VersionChangedEventHandler VersionChanged
 		{
-			if (unchecked(_enumeratorCount++) == 0)
+			[MethodImpl(MethodImplOptions.AggressiveInlining)]
+			add 
+			{ 
+				_versionChanged += value;
+				if (!IsVersioned)
+				{
+					IsVersioned = true;
+				}
+			}
+
+			[MethodImpl(MethodImplOptions.AggressiveInlining)]
+			remove
 			{
-				IsVersioned = true;
+				_versionChanged -= value;
+				if (_versionChanged == null)
+				{
+					IsVersioned = false;
+				}
 			}
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public void RemoveEnumerator()
+		public void Inc()
 		{
-			if (unchecked(--_enumeratorCount) == 0)
+			if (IsVersioned)
 			{
-				IsVersioned = false;
+				_versionChanged!();
 			}
+			//_ = unchecked(Version++);
 		}
 
+		//[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		//public RecyclableCollectionVersion AddEnumerator()
+		//{
+		//	if (unchecked(_enumeratorCount++) == 0)
+		//	{
+		//		IsVersioned = true;
+		//	}
+
+		//	return this;
+		//}
+
+		//[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		//public void RemoveEnumerator()
+		//{
+		//	if (unchecked(--_enumeratorCount) == 0)
+		//	{
+		//		IsVersioned = false;
+		//	}
+		//}
+
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public RecyclableCollectionVersion Reset()
 		{
 			IsVersioned = false;
-			Version = 0;
-			_enumeratorCount = 0;
+			//Version = 0;
+			//_enumeratorCount = 0;
 			return this;
 		}
 	}

Recyclable.Collections/RecyclableList.Enumerator.cs

@@ -1,79 +1,166 @@
 using System.Collections;
+using System.Diagnostics.Contracts;
+using System.Runtime.CompilerServices;
+using System.Runtime.ConstrainedExecution;
 
 namespace Recyclable.Collections
 {
-	public class RecyclableListEnumerator<T> : IEnumerator<T>
+	public partial class RecyclableList<T>
 	{
-		private static void ThrowListModifiedException() => throw new InvalidOperationException("Can't move to the next item, because the collection was modified. You must restart the enumeration by calling Reset(), if you want to enumerate the collection again");
 
-		private int _currentIndex = RecyclableDefaults.ItemNotFoundIndex;
-		private RecyclableList<T>? _list;
-		private RecyclableCollectionVersion? _listVersion;
-		private ulong _version;
-
-		private T? _current;
-
-		public RecyclableListEnumerator(RecyclableList<T> list)
+		public struct Enumerator : IEnumerator<T>, IEnumerator
 		{
-			_list = list;
-			_listVersion = list._version;
-			_listVersion!.AddEnumerator();
-			_version = _listVersion!.Version;
-		}
+#nullable disable
+			private readonly RecyclableList<T> _list;
+			private int _currentIndex;
+			private T _current;
 
-		public T Current => _current ?? throw new InvalidOperationException("The enumerator wasn't initialized. You need to call MoveNext() before getting the current iterator value");
-		object? IEnumerator.Current => _current;
+			//[Pure]
+			//private readonly int _listCount;
+			//private readonly int _listCountMinus1;
+			//private readonly T[] _memoryBlock;
+			//private bool _endOfCollectionReached;
 
-		public void Dispose()
-		{
-			if (_listVersion != null)
+			//private RecyclableCollectionVersion _listVersion;
+			//private ulong _enumeratorVersion;
+			//private bool _isVersionChanged;
+
+			//private void VersionChanged() => _isVersionChanged = true;
+
+			//internal RecyclableListEnumeratorPool? _pool;
+			//internal bool _returned;
+
+			//public RecyclableListEnumerator()
+			//{
+			//}
+
+			//[Pure]
+			internal Enumerator(RecyclableList<T> list)
 			{
-				_listVersion.RemoveEnumerator();
-				_listVersion = null;
+				_current = default;
+				_currentIndex = 0;
+				_list = list;
+				//_memoryBlock = list._memoryBlock;
+				//_listCount = list._count;
+				//_listVersion = list._version!;
+				//_listVersion.VersionChanged += VersionChanged;
+				//_enumeratorVersion = _listVersion.Version;
 			}
 
-			if (_list != null)
+			//{
+			//	//[MethodImpl(MethodImplOptions.AggressiveInlining)]
+			//	get =>
+			//			//if (_currentIndex < 0)
+			//			//{
+			//			//	ThrowHelper.ThrowInvalidOperationException("The enumerator wasn't initialized. You need to call MoveNext() before getting the current iterator value");
+			//			//}
+			//			//else
+			//			//if (_endOfCollectionReached)
+			//			//{
+			//			//	throw new InvalidOperationException("The enumerator reached the end of the collection. You need to call Reset(), if you want to enumerate the collection again");
+			//			//}
+			//			//else
+			//			//{
+			//			//if (_currentIndex < 0)
+			//			//{
+			//			//	ThrowHelper.ThrowInvalidOperationException("The enumerator wasn't initialized. You need to call MoveNext() before getting the current iterator value");
+			//			//}
+			//			//else
+			//			_memoryBlock[_currentIndex];//}
+			//}
+
+			//[Pure]
+			public readonly void Dispose()
 			{
-				_list = null;
+				//				if (_listVersion != null)
+				//				{
+				//					_listVersion.VersionChanged -= VersionChanged;
+				//					//_listVersion.RemoveEnumerator(this);
+				//#nullable disable
+				//					_listVersion = null;
+				//#nullable restore
+				//				}
+
+				//if (_pool != null)
+				//{
+				//	if (!_returned)
+				//	{
+				//		_returned = true;
+				//		_pool?.Return(this);
+				//	}
+				//}
+				//else
+				//{
+				//_memoryBlock = null;
+					//GC.SuppressFinalize(this);
+				//}
 			}
 
-			GC.SuppressFinalize(this);
-		}
-
-		public bool MoveNext()
-		{
-			if (_list != null)
+			//[MethodImpl(MethodImplOptions.AggressiveInlining)]
+			public bool MoveNext()
 			{
-				if (_list._version!.Version != _version)
-				{
-					ThrowListModifiedException();
-					return false;
-				}
-				else if (_currentIndex < _list.Count - 1)
+				var list = _list;
+				//if (_isVersionChanged)
+				//{
+				//	ThrowHelper.ThrowListModifiedException();
+				//	return false;
+				//}
+				//else
+				if (_currentIndex < list._count)
 				{
+					_current = list._memoryBlock[_currentIndex];
 					_currentIndex++;
-					_current = _list[_currentIndex];
 					return true;
 				}
-				else
-				{
-					return false;
-				}
-			}
-			else
-			{
+
+				//else if (!_endOfCollectionReached)
+				//{
+				//	_endOfCollectionReached = true;
+				//	return false;
+				//}
+
+				_current = default;
 				return false;
 			}
-		}
 
-		public void Reset()
-		{
-			_currentIndex = RecyclableDefaults.ItemNotFoundIndex;
-			_current = default;
-			if (_list != null)
+#nullable restore
+			public T Current => _current;
+			object IEnumerator.Current => _current;
+#nullable disable
+
+			//[MethodImpl(MethodImplOptions.AggressiveInlining)]
+			void IEnumerator.Reset()
 			{
-				_version = _list._version!.Version;
+				_currentIndex = 0;
+				_current = default;
 			}
+
+			//_endOfCollectionReached = false;
+			//if (_isVersionChanged)
+			//{
+			//	
+			//_enumeratorVersion = _listVersion!.Version;
+			//	_isVersionChanged = false;
+			//}
+
+			//internal RecyclableListEnumerator Reset(RecyclableListEnumeratorPool pool, RecyclableList<T> list)
+			//{
+			//	_returned = false;
+			//	if (_pool != pool)
+			//	{
+			//		_pool = pool;
+			//	}
+
+			//	_currentIndex = RecyclableDefaults.ItemNotFoundIndex;
+			//	_listVersion = list._version!;
+			//	_enumeratorVersion = _listVersion!.Version;
+			//	list._version!.AddEnumerator();
+			//	return this;
+			//}
+
+			//[Pure]
+			//public object Clone() => MemberwiseClone();
 		}
 	}
+#nullable restore
 }

Recyclable.Collections/RecyclableList.IList.cs

@@ -7,7 +7,9 @@ namespace Recyclable.Collections
 		public bool IsFixedSize => false;
 		public bool IsSynchronized => false;
 
+		[NonSerialized]
 		private object? _syncRoot;
+
 		public object SyncRoot
 		{
 			get
@@ -39,7 +41,7 @@ namespace Recyclable.Collections
 				}
 				else
 				{
-					ThrowArgumentOutOfRangeException(nameof(value), $"Argument is invalid. {(value != null ? "List element type is incompatible with the given value" : "Element is null and the list doesn't allow null values.")}");
+					ThrowHelper.ThrowArgumentOutOfRangeException(nameof(value), $"Argument is invalid. {(value != null ? "List element type is incompatible with the given value" : "Element is null and the list doesn't allow null values.")}");
 				}
 			}
 		}
@@ -58,7 +60,7 @@ namespace Recyclable.Collections
 			}
 			else
 			{
-				ThrowArgumentOutOfRangeException(nameof(value), $"Argument is invalid. {(value != null ? "List element type is incompatible with the given value" : "Element is null and the list doesn't allow null values.")}");
+				ThrowHelper.ThrowArgumentOutOfRangeException(nameof(value), $"Argument is invalid. {(value != null ? "List element type is incompatible with the given value" : "Element is null and the list doesn't allow null values.")}");
 				return RecyclableDefaults.ItemNotFoundIndex;
 			}
 		}
@@ -91,7 +93,7 @@ namespace Recyclable.Collections
 			}
 			else
 			{
-				ThrowArgumentOutOfRangeException(nameof(value), $"Argument is invalid. {(value != null ? "List element type is incompatible with the given value" : "Element is null and the list doesn't allow null values.")}");
+				ThrowHelper.ThrowArgumentOutOfRangeException(nameof(value), $"Argument is invalid. {(value != null ? "List element type is incompatible with the given value" : "Element is null and the list doesn't allow null values.")}");
 			}
 		}
 
@@ -109,7 +111,7 @@ namespace Recyclable.Collections
 			}
 			else
 			{
-				ThrowArgumentOutOfRangeException(nameof(value), $"Argument is invalid. {(value != null ? "List element type is incompatible with the given value" : "Element is null and the list doesn't allow null values.")}");
+				ThrowHelper.ThrowArgumentOutOfRangeException(nameof(value), $"Argument is invalid. {(value != null ? "List element type is incompatible with the given value" : "Element is null and the list doesn't allow null values.")}");
 			}
 		}
 

Recyclable.Collections/RecyclableList.cs

@@ -5,13 +5,13 @@ using System.Runtime.CompilerServices;
 
 namespace Recyclable.Collections
 {
-	public partial class RecyclableList<T> : IList<T>, IReadOnlyList<T>, IDisposable
+	[Serializable]
+	public sealed partial class RecyclableList<T> : IList<T>, IReadOnlyList<T>, IList, IDisposable
 	{
 		private static readonly ArrayPool<T> _arrayPool = ArrayPool<T>.Create();
 		private static readonly bool _defaultIsNull = default(T) == null;
 		protected static readonly bool NeedsClearing = !typeof(T).IsValueType;
 	
-		private static void ThrowArgumentOutOfRangeException(in string argumentName, in string message) => throw new ArgumentOutOfRangeException(argumentName, message);
 		public static explicit operator ReadOnlySpan<T>(RecyclableList<T> source) => new(source._memoryBlock, 0, source.Count);
 
 		protected T[] _memoryBlock;
@@ -224,23 +224,23 @@ namespace Recyclable.Collections
 		}
 
 		protected int _count;
-		public int Count
-		{
-			[MethodImpl(MethodImplOptions.AggressiveInlining)]
-			get => _count;
+		public int Count => _count;
+		//{
+		//	[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		//	get => _count;
 
-			[MethodImpl(MethodImplOptions.AggressiveInlining)]
-			// TODO: Clear items if we're decreasing the size of the list, if T is reference type
-			set
-			{
-				_count = value;
+		//	[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		//	// TODO: Clear items if we're decreasing the size of the list, if T is reference type
+		//	set
+		//	{
+		//		_count = value;
 
-				if (_version?.IsVersioned ?? false)
-				{
-					_version.Inc();
-				}
-			}
-		}
+		//		if (_version?.IsVersioned ?? false)
+		//		{
+		//			_version.Inc();
+		//		}
+		//	}
+		//}
 
 		public bool IsReadOnly => false;
 
@@ -397,12 +397,12 @@ namespace Recyclable.Collections
 			var sourceItemsCount = items.LongCount;
 			if (sourceItemsCount > int.MaxValue)
 			{
-				ThrowArgumentOutOfRangeException(nameof(items), $"The number of items exceeds the maximum capacity of {nameof(RecyclableList<T>)}, equal {int.MaxValue}, equal {int.MaxValue}. Please consider using {nameof(RecyclableLongList<T>)}, instead");
+				ThrowHelper.ThrowArgumentOutOfRangeException(nameof(items), $"The number of items exceeds the maximum capacity of {nameof(RecyclableList<T>)}, equal {int.MaxValue}, equal {int.MaxValue}. Please consider using {nameof(RecyclableLongList<T>)}, instead");
 			}
 
 			if (_count + sourceItemsCount > int.MaxValue)
 			{
-				ThrowArgumentOutOfRangeException(nameof(items), $"The total number of items in source and target table exceeds the maximum capacity of {nameof(RecyclableList<T>)}, equal {int.MaxValue}. Please consider using {nameof(RecyclableLongList<T>)}, instead");
+				ThrowHelper.ThrowArgumentOutOfRangeException(nameof(items), $"The total number of items in source and target table exceeds the maximum capacity of {nameof(RecyclableList<T>)}, equal {int.MaxValue}. Please consider using {nameof(RecyclableLongList<T>)}, instead");
 			}
 
 			int targetCapacity = _count + (int)sourceItemsCount;
@@ -571,7 +571,7 @@ namespace Recyclable.Collections
 		{
 			if (index >= _count)
 			{
-				ThrowArgumentOutOfRangeException(nameof(index), $"Provided value {index} exceeds the no. of items on the list {_count}");
+				ThrowHelper.ThrowArgumentOutOfRangeException(nameof(index), $"Provided value {index} exceeds the no. of items on the list {_count}");
 			}
 
 			_count--;
@@ -593,19 +593,16 @@ namespace Recyclable.Collections
 			}
 		}
 
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public IEnumerator<T> GetEnumerator()
-		{
-			_version ??= RecyclableCollectionVersionPool.Shared.Get();
-			return new RecyclableListEnumerator<T>(this);
-		}
+		public Enumerator GetEnumerator() => new Enumerator(this);
+		//[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		IEnumerator IEnumerable.GetEnumerator() =>
+			//_version ??= new(); // RecyclableCollectionVersionPool.Shared.Get();
+			new Enumerator(this);//return RecyclableListEnumeratorPool.Shared.Get(this);
 
-		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		IEnumerator IEnumerable.GetEnumerator()
-		{
-			_version ??= RecyclableCollectionVersionPool.Shared.Get();
-			return new RecyclableListEnumerator<T>(this);
-		}
+		//[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		IEnumerator<T> IEnumerable<T>.GetEnumerator() =>
+			//_version ??= new(); // RecyclableCollectionVersionPool.Shared.Get();
+			new Enumerator(this);//return RecyclableListEnumeratorPool.Shared.Get(this);
 
 		public void Dispose()
 		{
@@ -620,9 +617,9 @@ namespace Recyclable.Collections
 
 				if (_version != null)
 				{
-					var toReturn = _version;
+					//var toReturn = _version;
 					_version = null;
-					RecyclableCollectionVersionPool.Shared.Return(toReturn);
+					//RecyclableCollectionVersionPool.Shared.Return(toReturn);
 				}
 
 				GC.SuppressFinalize(this);

Recyclable.Collections/RecyclableLongList.Enumerator.cs

@@ -0,0 +1,149 @@
+using System.Collections;
+
+namespace Recyclable.Collections
+{
+	public sealed class RecyclableLongListEnumerator<T> : IEnumerator<T>
+	{
+		public static void ThrowListModifiedException() => throw new InvalidOperationException("Can't move to the next item, because the collection was modified. You must restart the enumeration by calling Reset(), if you want to enumerate the collection again");
+
+		private int _blockSize;
+		private int _blockSizeMinus1;
+		private int _currentBlockIndex = 0;
+		private int _currentIndex = RecyclableDefaults.ItemNotFoundIndex;
+		private int _lastBlockWithData;
+		private RecyclableLongList<T>? _list;
+		private RecyclableCollectionVersion? _listVersion;
+		private T[][] _memoryBlocks;
+		private int _nextItemBlockIndex;
+		private int _nextItemIndex;
+		//private ulong _version;
+		private bool _isVersionChanged;
+		private void VersionChanged() => _isVersionChanged = true;
+
+		private T? _current;
+
+		public RecyclableLongListEnumerator(RecyclableLongList<T> list)
+		{
+			_listVersion = list._version;
+			list._version!.VersionChanged += VersionChanged;
+			//_listVersion!.AddEnumerator();
+			_blockSize = list._blockSize;
+			_blockSizeMinus1 = list._blockSizeMinus1;
+			_lastBlockWithData = list._lastBlockWithData;
+			_list = list;
+			//_version = _listVersion!.Version;
+			_memoryBlocks = list._memoryBlocks;
+			_nextItemBlockIndex = list._nextItemBlockIndex;
+			_nextItemIndex = _lastBlockWithData == _nextItemBlockIndex ? _list._nextItemIndex : _blockSize;
+		}
+
+		public T Current => _current ?? throw new InvalidOperationException("The enumerator wasn't initialized. You need to call MoveNext() before getting the current iterator value");
+		object? IEnumerator.Current => _current;
+
+		public void Dispose()
+		{
+			if (_listVersion != null)
+			{
+				_listVersion.VersionChanged -= VersionChanged;
+				//_listVersion.RemoveEnumerator();
+				_listVersion = null;
+			}
+
+			if (_list != null)
+			{
+				_list = null;
+			}
+
+			GC.SuppressFinalize(this);
+		}
+
+		public bool MoveNext()
+		{
+			if (_list != null)
+			{
+				if (_isVersionChanged)
+				{
+					_current = default;
+					ThrowListModifiedException();
+					return false;
+				}
+				else if (_currentBlockIndex < _lastBlockWithData)
+				{
+					if (_currentIndex < _blockSizeMinus1)
+					{
+						_currentIndex++;
+					}
+					else
+					{
+						_currentIndex = 0;
+						_currentBlockIndex++;
+						if (_currentBlockIndex == _lastBlockWithData && _currentIndex >= _nextItemIndex)
+						{
+							_current = default;
+							return false;
+						}
+					}
+
+					_current = _memoryBlocks[_currentBlockIndex][_currentIndex];
+					return true;
+				}
+				else if (_currentBlockIndex == _lastBlockWithData && !(_currentIndex >= _nextItemIndex - 1))
+				{
+					_currentIndex++;
+					_current = _memoryBlocks[_currentBlockIndex][_currentIndex];
+					return true;
+				}
+				else
+				{
+					_current = default;
+					return false;
+				}
+			}
+			else
+			{
+				_current = default;
+				return false;
+			}
+		}
+
+		public void Reset()
+		{
+			_currentBlockIndex = 0;
+			_currentIndex = RecyclableDefaults.ItemNotFoundIndex;
+			_current = default;
+			if (_isVersionChanged)
+			{
+				//_blockSize = _list!._blockSize;
+				//_blockSizeMinus1 = _list._blockSizeMinus1;
+				_isVersionChanged = false;
+				//_lastBlockWithData = _list!._lastBlockWithData;
+				//_listVersion = _list._version;
+				//_memoryBlocks = _list._memoryBlocks;
+				//_nextItemBlockIndex = _list._nextItemBlockIndex;
+				//_nextItemIndex = _lastBlockWithData == _nextItemBlockIndex ? _list._nextItemIndex : _blockSize;
+				//_version = _listVersion!.Version;
+			}
+		}
+
+		internal RecyclableLongListEnumerator<T> Init()
+		{
+			_currentBlockIndex = 0;
+			_currentIndex = RecyclableDefaults.ItemNotFoundIndex;
+			_current = default;
+			if (_list != null)
+			{
+				_blockSize = _list._blockSize;
+				_blockSizeMinus1 = _list._blockSizeMinus1;
+				_isVersionChanged = false;
+				_lastBlockWithData = _list._lastBlockWithData;
+				_listVersion = _list._version;
+				_memoryBlocks = _list._memoryBlocks;
+				_nextItemBlockIndex = _list._nextItemBlockIndex;
+				_nextItemIndex = _lastBlockWithData == _nextItemBlockIndex ? _list._nextItemIndex : _blockSize;
+				//_version = _listVersion!.Version;
+			}
+
+			return this;
+		}
+	}
+}

Recyclable.Collections/RecyclableLongList.cs

@@ -22,7 +22,7 @@ namespace Recyclable.Collections
 		internal int _blockSize;
 		internal byte _blockSizePow2BitShift;
 		internal int _blockSizeMinus1;
-		private int _nextItemBlockIndex;
+		internal int _nextItemBlockIndex;
 		internal int _nextItemIndex;
 		private int _reservedBlockCount;
 
@@ -36,12 +36,34 @@ namespace Recyclable.Collections
 		public long Capacity
 		{
 			get => _capacity;
-			protected set => _capacity = value;
+			protected set
+			{
+				_capacity = value;
+
+				if (_version?.IsVersioned ?? false)
+				{
+					_version.Inc();
+				}
+			}
 		}
 
-		public int Count => checked((int)_longCount);
-		public bool IsReadOnly { get; }
-		private int _lastBlockWithData = RecyclableDefaults.ItemNotFoundIndex;
+		public int Count
+		{
+			get => checked((int)_longCount);
+
+			set
+			{
+				_longCount = value;
+
+				if (_version?.IsVersioned ?? false)
+				{
+					_version.Inc();
+				}
+			}
+		}
+
+		public bool IsReadOnly => false;
+		internal int _lastBlockWithData = RecyclableDefaults.ItemNotFoundIndex;
 		public int LastBlockWithData => _lastBlockWithData;
 
 		internal long _longCount;
@@ -49,7 +71,15 @@ namespace Recyclable.Collections
 		public long LongCount
 		{
 			get => _longCount;
-			set => _longCount = value;
+			set
+			{
+				_longCount = value;
+
+				if (_version?.IsVersioned ?? false)
+				{
+					_version.Inc();
+				}
+			}
 		}
 
 		public int ReservedBlockCount => _reservedBlockCount;
@@ -58,6 +88,9 @@ namespace Recyclable.Collections
 		public byte BlockSizePow2BitShift => _blockSizePow2BitShift;
 		public int NextItemBlockIndex => _nextItemBlockIndex;
 		public int NextItemIndex => _nextItemIndex;
+		
+		internal RecyclableCollectionVersion? _version;
+		public RecyclableCollectionVersion? Version => _version;
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
 		private static void CopyFollowingItems(RecyclableLongList<T> list, long destinationItemIndex)
@@ -631,16 +664,32 @@ namespace Recyclable.Collections
 		public T this[long index]
 		{
 			get => _memoryBlocks[index >> _blockSizePow2BitShift][index & _blockSizeMinus1];
-			set => new Span<T>(_memoryBlocks[checked((int)(index >> _blockSizePow2BitShift))])[checked((int)(index & _blockSizeMinus1))] = value;
+			set
+			{
+				new Span<T>(_memoryBlocks[checked((int)(index >> _blockSizePow2BitShift))])[checked((int)(index & _blockSizeMinus1))] = value;
+
+				if (_version?.IsVersioned ?? false)
+				{
+					_version.Inc();
+				}
+			}
 		}
 
 		public T this[int index]
 		{
 			get => _memoryBlocks[index >> _blockSizePow2BitShift][index & _blockSizeMinus1];
-			set => new Span<T>(_memoryBlocks[index >> _blockSizePow2BitShift])[index & _blockSizeMinus1] = value;
+			set
+			{
+				new Span<T>(_memoryBlocks[index >> _blockSizePow2BitShift])[index & _blockSizeMinus1] = value;
+
+				if (_version?.IsVersioned ?? false)
+				{
+					_version.Inc();
+				}
+			}
 		}
 
-		public T[][] AsArray { get => _memoryBlocks; }
+		public T[][] AsArray => _memoryBlocks;
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public void Add(T item)
@@ -667,6 +716,11 @@ namespace Recyclable.Collections
 			}
 
 			_longCount++;
+
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
 		}
 
 		public void AddRange(in T[] items)
@@ -715,6 +769,11 @@ namespace Recyclable.Collections
 			_nextItemIndex = itemsSpan.Length;
 			_longCount = targetCapacity;
 			_lastBlockWithData = targetBlockIndex;
+
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
 		}
 
 		public void AddRange(RecyclableList<T> items)
@@ -755,6 +814,11 @@ namespace Recyclable.Collections
 			_longCount = targetCapacity;
 			_nextItemBlockIndex = targetBlockIndex;
 			_lastBlockWithData = targetBlockIndex - (itemsSpan.Length > 0 ? 0 : 1);
+
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
 		}
 
 		public void AddRange(ReadOnlySpan<T> itemsSpan)
@@ -802,6 +866,11 @@ namespace Recyclable.Collections
 			_nextItemIndex = itemsSpan.Length;
 			_longCount = targetCapacity;
 			_lastBlockWithData = targetBlockIndex;
+
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
 		}
 
 		public void AddRange(RecyclableLongList<T> items)
@@ -874,6 +943,11 @@ namespace Recyclable.Collections
 			}
 
 			_longCount = targetCapacity;
+
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
 		}
 
 		public void AddRange(List<T> items)
@@ -921,6 +995,11 @@ namespace Recyclable.Collections
 			_nextItemBlockIndex = targetBlockIndex;
 			_longCount = targetCapacity;
 			_lastBlockWithData = targetBlockIndex - (_nextItemIndex > 0 ? 0 : 1);
+
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
 		}
 
 		public void AddRange(IList<T> items)
@@ -975,6 +1054,11 @@ namespace Recyclable.Collections
 				{
 					_defaultBlockArrayPool.Return(itemsBuffer, NeedsClearing);
 				}
+
+				if (_version?.IsVersioned ?? false)
+				{
+					_version.Inc();
+				}
 			}
 		}
 
@@ -983,40 +1067,41 @@ namespace Recyclable.Collections
 			if (source is RecyclableLongList<T> sourceRecyclableLongList)
 			{
 				AddRange(sourceRecyclableLongList);
-				return;
 			}
-
-			if (source is RecyclableList<T> sourceRecyclableList)
+			else if (source is RecyclableList<T> sourceRecyclableList)
 			{
 				AddRange(sourceRecyclableList);
-				return;
 			}
-
-			if (source is T[] sourceArray)
+			else if (source is T[] sourceArray)
 			{
 				AddRange(sourceArray);
-				return;
 			}
-
-			if (source is List<T> sourceList)
+			else if (source is List<T> sourceList)
 			{
 				AddRange(sourceList);
-				return;
 			}
-
-			if (source is IList<T> sourceIList)
+			else if (source is IList<T> sourceIList)
 			{
 				AddRange(sourceIList);
-				return;
 			}
-
-			if (source.TryGetNonEnumeratedCount(out var requiredAdditionalCapacity))
+			else if (source.TryGetNonEnumeratedCount(out var requiredAdditionalCapacity))
 			{
 				AddRangeWithKnownCount(source, requiredAdditionalCapacity);
-				return;
-			}
 
-			AddRangeEnumerated(source, growByCount);
+				if (_version?.IsVersioned ?? false)
+				{
+					_version.Inc();
+				}
+			}
+			else
+			{
+				AddRangeEnumerated(source, growByCount);
+
+				if (_version?.IsVersioned ?? false)
+				{
+					_version.Inc();
+				}
+			}
 		}
 
 		public void Clear()
@@ -1045,6 +1130,11 @@ namespace Recyclable.Collections
 			_nextItemIndex = 0;
 			_lastBlockWithData = RecyclableDefaults.ItemNotFoundIndex;
 			_longCount = 0;
+
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -1075,7 +1165,17 @@ namespace Recyclable.Collections
 
 		public void CopyTo(T[] array, int arrayIndex) => RecyclableLongList<T>.RecyclableLongListHelpers.CopyTo(_memoryBlocks, 0, _blockSize, _longCount, array, arrayIndex);
 
-		public IEnumerator<T> GetEnumerator() => RecyclableLongList<T>.RecyclableLongListHelpers.Enumerate(_memoryBlocks, _blockSize, LongCount).GetEnumerator();
+		public IEnumerator<T> GetEnumerator()
+		{
+			_version ??= new();
+			return new RecyclableLongListEnumerator<T>(this);
+		}
+
+		IEnumerator IEnumerable.GetEnumerator()
+		{
+			_version ??= new();
+			return new RecyclableLongListEnumerator<T>(this);
+		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
 		public int IndexOf(T item)
@@ -1188,6 +1288,11 @@ namespace Recyclable.Collections
 #pragma warning restore CS8601
 				}
 
+				if (_version?.IsVersioned ?? false)
+				{
+					_version.Inc();
+				}
+
 				return true;
 			}
 
@@ -1217,6 +1322,11 @@ namespace Recyclable.Collections
 			}
 
 			_lastBlockWithData--;
+
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
@@ -1256,6 +1366,11 @@ namespace Recyclable.Collections
 				_memoryBlocks[_nextItemBlockIndex][_nextItemIndex] = default;
 #pragma warning restore CS8601
 			}
+
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
@@ -1294,9 +1409,12 @@ namespace Recyclable.Collections
 				_memoryBlocks[_nextItemBlockIndex][_nextItemIndex] = default;
 #pragma warning restore CS8601
 			}
-		}
 
-		IEnumerator IEnumerable.GetEnumerator() => RecyclableLongList<T>.RecyclableLongListHelpers.Enumerate(_memoryBlocks, _blockSize, LongCount).GetEnumerator();
+			if (_version?.IsVersioned ?? false)
+			{
+				_version.Inc();
+			}
+		}
 
 		~RecyclableLongList()
 		{
@@ -1315,6 +1433,13 @@ namespace Recyclable.Collections
 					_memoryBlocksPool.Return(_memoryBlocks, NeedsClearing);
 				}
 
+				if (_version != null)
+				{
+					//var toReturn = _version;
+					_version = null;
+					//RecyclableCollectionVersionPool.Shared.Return(toReturn);
+				}
+
 				GC.SuppressFinalize(this);
 			}
 		}

Recyclable.Collections/ThrowHelper.cs

@@ -0,0 +1,23 @@
+namespace Recyclable.Collections
+{
+	internal static class ThrowHelper
+	{
+		/// <summary>
+		/// This is a helper method to throw <see cref="InvalidOperationException"/>, thrown when the collection was modified during enumeration.
+		/// </summary>
+		/// <exception cref="InvalidOperationException">Always</exception>
+		public static void ThrowListModifiedException() => throw new InvalidOperationException("Can't move to the next item, because the collection was modified. You must restart the enumeration by calling Reset(), if you want to enumerate the collection again");
+
+		/// <summary>
+		/// This is a helper method to throw <see cref="InvalidOperationException"/> with the given message.
+		/// </summary>
+		/// <exception cref="InvalidOperationException">Always</exception>
+		public static void ThrowInvalidOperationException(in string message) => throw new InvalidOperationException(message);
+
+		/// <summary>
+		/// This is a helper method to throw <see cref="ArgumentOutOfRangeException"/> with the given message.
+		/// </summary>
+		/// <exception cref="ArgumentOutOfRangeException">Always</exception>
+		public static void ThrowArgumentOutOfRangeException(in string argumentName, in string message) => throw new ArgumentOutOfRangeException(argumentName, message);
+	}
+}