Виртуальные методы

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

namespace Study
{
    class Program
    {
        static void Main(string[] args)
        {
            DoAction(new Trader());
            DoAction(new NPC());
        }
        static void DoAction(NPC npc)
        {
            npc.Action();
        }
    }
    class NPC
    {
        public virtual void Action()
        {
            Console.WriteLine("I,m npc ");
        }

    }
    class Trader : NPC
    {
        public override void Action()
        {
            Console.WriteLine("I,m trader");

        }

    }
    class Warrior : NPC
    {

    }
}