class Program
    {
        static void Main(string[] args)
        {
            ShopCart sc = new ShopCart(new ProudctA());
            sc.doSomthing();
            sc = new ShopCart(new ProudctB());
            sc.doSomthing();
        }
    }
    public class ShopCart {
        public IStrategy strategr;
        public ShopCart(IStrategy strategr) {
            this.strategr = strategr;
        }
        public void doSomthing()
        {
            this.strategr.compute();
        }
    }
    public interface IStrategy
    {

         void compute();
    }
    public class ProudctA : IStrategy {

        public void compute()
        {
            Console.WriteLine("商品折扣价100");
        }
    }
    public class ProudctB: IStrategy
    {

        public void compute()
        {
            Console.WriteLine("商品折扣价200");
        }
    }