using System;

using System.Threading;

​

public class Program

{

    public static void Main()

    {

        Item itemInfo = new Item{Name = "ProductA", Price = 10, StockInHand = 14};

        itemInfo.Alert += Order.RefillRequest;

        itemInfo.StockInHand -= 5;

        Thread.Sleep(5 * 1000);

        itemInfo.StockInHand -= 5;

    }

}

​

internal class Item

{

    internal event Action<object> Alert;

    private int _stockInHand;

    private int _itemId = +1;

    internal int ItemId

    {

        get

        {

            return _itemId;

        }

​

        private set

        {

            _itemId = value;

        }

    }

​

    internal string Name

    {

        get;

        set;

    }

​

    internal int Price

    {

        get;

        set;

    }

​

    internal int StockInHand

    {

        get

        {

            return _stockInHand;

        }

​

        set

        {

            _stockInHand = value;

            if (_stockInHand < 5)

            {

                if (Alert != null)

                {

                    Alert(this);

                }

            }

            else

            {

                Console.WriteLine("Item instock is {0}", _stockInHand);

            }

        }

    }

}

​

internal static class Order

{

    internal static void RefillRequest(object obj)

    {

        //if (obj is Item item)  DotNet Fiddle not able to compile so commented but in visual studio it runs

        {

            Console.WriteLine("Item in stock in hand has reduced less than five. Please refill"); //, item.StockInHand

        }

    }

}