using System;

using System.Linq;

using System.Collections.Generic;

​

public class Program

{

    public interface IMenuItem

    {

        string Name { get; set; }

        int Price { get; set; }

    }

    public class Pizza : IMenuItem

    {

        public string Name { get; set; }

        public int Price { get; set; }

        // Maybe other pizza-related stuff here

    }

    public class Burger : IMenuItem

    {

        public string Name { get; set; }

        public int Price { get; set; }

        // Maybe other burger-related stuff here

    }

    public static void Main()

    {

        IEnumerable<Pizza> pizzas = new Pizza[]

        {

            new Pizza { Name = "Pizza1", Price = 100 },

            new Pizza { Name = "Pizza2", Price = 200 }

        };

        IEnumerable<Burger> burgers = new Burger[]

        {

            new Burger { Name = "Burger1", Price = 100 },

            new Burger { Name = "Burger2", Price = 200 }

        };

        IEnumerable<IMenuItem> items = pizzas.Concat<IMenuItem>(burgers);

        foreach (var x in items)

            Console.WriteLine(x.Name);

    }

}