using System;

public class Program

{

    public static void Main(string[] args)

    {

        Console.WriteLine("Starting OrderProcessingService Override Test");

        Functions functions = new Functions();

        IOrderProcessingService orderProcessingService = new OrderProcessingService(functions);

        ProcessingService(orderProcessingService);

    }

​

    public partial interface IOrderProcessingService

    {

        public int MoveShoppingCartItemsToOrderItems();

    }

    IOrderProcessingService _orderProcessingService;

    public void ProcessingService(IOrderProcessingService orderProcessingService)

    {

        _orderProcessingService = orderProcessingService;

        Console.WriteLine();

        Console.WriteLine("Trying to call override");

        int number = orderProcessingService.MoveShoppingCartItemsToOrderItems();        

        Console.WriteLine(number);

​

        Console.WriteLine("Calling override function directly");

    }

​

    public partial class OrderProcessingService : IOrderProcessingService

    {   

        Functions _functions;

        public OrderProcessingService(Functions functions) : base()

        {

            _functions = functions;

            Console.WriteLine("OrderProcessingService Initialisation");

        }       

        public virtual int MoveShoppingCartItemsToOrderItems()

        {

            return _functions.Get(1);

        }

    }

    public class CustomOrderProcessingService : OrderProcessingService

    {

        Functions _functions;

        public CustomOrderProcessingService(Functions functions) : base(functions)

        {

            _functions = functions;

            Console.WriteLine("CustomOrderProcessingService Initialisation");

        }       

​

        public override int MoveShoppingCartItemsToOrderItems()

        {

            return _functions.Get(2);

        }

    }

​

    public class Functions

    {

        public int Get(int number)

        {

            return number;

        }

    }

}

​