Performance & standardization improvements.

Business logic fixes.
RecyclableQueue & RecyclableStack added - pending improvements.

Recyclable.Collections/RecyclableStack.cs

@@ -0,0 +1,86 @@
+using System.Collections;
+
+namespace Recyclable.Collections
+{
+	public class RecyclableStack<T> : IList<T>, IDisposable
+	{
+		private bool _disposedValue;
+		private readonly int _blockSize;
+
+		protected RecyclableList<T> List { get; }
+		public int Count => List.Count;
+		public long LongCount
+		{
+			get => List.LongCount;
+			set => List.LongCount = value;
+		}
+
+		public bool IsReadOnly => List.IsReadOnly;
+
+		public T this[int index] { get => this[(long)index]; set => this[(long)index] = value; }
+		public T this[long index] { get => List[index]; set => List[index] = value; }
+
+		public RecyclableStack(int blockSize = RecyclableDefaults.BlockSize)
+		{
+			_blockSize = blockSize;
+			List = new(blockSize);
+		}
+
+		public RecyclableStack(IEnumerable<T> list, int blockSize = RecyclableDefaults.BlockSize)
+		{
+			_blockSize = blockSize;
+			List = new(list, blockSize);
+		}
+
+		public RecyclableStack(RecyclableList<T> list, int blockSize = RecyclableDefaults.BlockSize)
+		{
+			_blockSize = blockSize;
+			List = new(list, blockSize);
+		}
+
+		public void Push(T item)
+		{
+			List.Add(item);
+		}
+
+		public T Pop()
+		{
+			var toRemove = List[LongCount - 1];
+			LongCount--;
+			if (List.Capacity - LongCount == _blockSize)
+			{
+				List.RemoveBlock(List.BlockCount - 1);
+			}
+
+			return toRemove;
+		}
+
+		public int IndexOf(T item) => List.IndexOf(item);
+		public long LongIndexOf(T item) => List.LongIndexOf(item);
+		public void Insert(int index, T item) => List.Insert(index, item);
+		public void RemoveAt(int index) => List.RemoveAt(index);
+		public void Add(T item) => List.Add(item);
+		public void Clear() => List.Clear();
+		public bool Contains(T item) => List.Contains(item);
+		public void CopyTo(T[] array, int arrayIndex) => List.CopyTo(array, arrayIndex);
+		public bool Remove(T item) => List.Remove(item);
+		public IEnumerator<T> GetEnumerator() => List.Reverse().GetEnumerator();
+		IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+		protected virtual void Dispose(bool disposing)
+		{
+			if (!_disposedValue)
+			{
+				Clear();
+				_disposedValue = true;
+			}
+		}
+
+		public void Dispose()
+		{
+			// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
+			Dispose(disposing: true);
+			GC.SuppressFinalize(this);
+		}
+	}
+}