ArrayList as Enumerable Extension

ArrayListExtension.cs

using System.Collections;
using System.Collections.Generic;

namespace System.CollectionsEx 
{

	public static class ArrayListExtensions
	{
		public static IEnumerable<T> AsEnumerable<T>(this ArrayList collection)
		{
			return new ArrayListEnumerable(collection).AsEnumerable<T>();
		}

		private class ArrayListEnumerable
		{
			private ArrayList collection;
			private bool AnyOfType;

			public ArrayListEnumerable(ArrayList collection)
			{
				this.collection = collection;
				AnyOfType = false;
			}

			public IEnumerable<T> AsEnumerable<T>()
			{
				foreach (var item in collection)
				{
					if (item is T)
					{
						if (AnyOfType != true)
						{
							AnyOfType = true;
						}
						yield return (T)item;
					}
				}
				if (!AnyOfType)
				{
					T thing = default(T);
					yield return thing;
				}
			}
		}
	}
}