using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    internal class DisposingEnumerator : IEnumerator<Item>

{

    private readonly List<IDisposable> deallocationQueue = new List<IDisposable>();

    private readonly IEnumerable<Item> source;

    private IEnumerator<Item> sourceEnumerator;

    public DisposingEnumerator(IEnumerable<Item> source)

    {

        this.source = source;

    }

​

    public bool MoveNext()

    {

        if (sourceEnumerator == null)

        {

            sourceEnumerator = source.GetEnumerator();

        }

        bool hasNext = sourceEnumerator.MoveNext();

        if (hasNext)

        {

            deallocationQueue.Add(Current);

        } 

        return hasNext;

    }

​

    public Item Current => sourceEnumerator.Current;

​

    object IEnumerator.Current => Current;

​

    public void Reset()

    {

        throw new NotSupportedException();

    }

​

    public void Dispose()

    {

        Console.WriteLine(deallocationQueue.Count);

        foreach (var item in deallocationQueue)

        {

            item.Dispose();

        }

    }

}

​

public class ItemCollection : IEnumerable<Item>, IDisposable

{

    private bool disposed = false;

    private IEnumerator<Item> enumerator;

​

    public ItemCollection(IEnumerable<Item> source)

    {

        this.enumerator = new DisposingEnumerator(source);

    }

​

    public IEnumerator<Item> GetEnumerator()

    {

        if (disposed)

        {

           throw new ObjectDisposedException("ItemCollection");

        }

        return enumerator;

    }

​

    IEnumerator IEnumerable.GetEnumerator()

    {

        return GetEnumerator();

    }

​

    // Will be not called from finalizer, but within "using" statement

    public void Dispose()

    {

        enumerator.Dispose();

        disposed = true;

    }

}

    public class Item : IDisposable

    {   

        private Guid Id = Guid.NewGuid();

        public void Dispose()

        {

            Console.WriteLine($"Disposed {Id}");

        }

    }

    public static void Main()

    {

        var items = Enumerable.Range(0, 10).Select(x => new Item());

​

    foreach (var item in new ItemCollection(items))

    {

        Console.WriteLine("Iteration");

    }

​

    }

}