Interfaces and class relations

Here is our partial class diagram

Here is the code

IFRed the interface

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace InterfacesExample
{
    public interface IFred
    {
         void Add(object o);
        void Edit(object o);
        void Remove(object o);

         List<object> GetList();
    }
}

---

Barney class

---

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace InterfacesExample
{
    class Barney:IFred
    {
        List<object> itemList;

        public Barney()
        {
            itemList = new List<object>();
        }


        public void Add(object o)
        {
            //Item i = (Item)o;
            itemList.Add(o);
        }

        public void Edit(object o)
        {
            throw new NotImplementedException();
        }

        public void Remove(object o)
        {
            throw new NotImplementedException();
        }

        public List<object> GetList()
        {
            return itemList;
        }
    }
}

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The Programclass

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the Item class

---

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace InterfacesExample
{
    class Item
    {
        public string Name { get; set; }
        public double Price { get; set; }
    }
}

---

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace InterfacesExample
{
    class Program
    {
        static void Main(string[] args)
        {
            Barney b = new Barney();
            Console.WriteLine("how many items?");
            int number = int.Parse(Console.ReadLine());
            for (int i = 0; i < number; i++)
            {
                Item item = new Item();
                Console.WriteLine("Enter item name");
                item.Name = Console.ReadLine();
                Console.WriteLine("Enter Price");
                item.Price = double.Parse(Console.ReadLine());
                b.Add(item);
            }

            Console.Clear();
            List<object> items = b.GetList();
            foreach(object o in items)
            {
                Item i = (Item)o;
       
                Console.WriteLine(i.Name + "  " + i.Price);
            }

            Console.ReadKey();
        }
    }
}