Decorator pattern คืออะไร

DefaultComputerSet1 basicComputer = new DefaultComputerSet1();
            ComputerUpgrade upgradeSet = new ComputerUpgrade(basicComputer);
            upgradeSet = new GeforceRTX2080(upgradeSet);
            upgradeSet = new CreativeSoundAE7(upgradeSet);


            Console.WriteLine("Description : " + upgradeSet.GetDescription());
            Console.WriteLine("Price : " + upgradeSet.GetPrice());
        

using System;

using AppKit;
using Foundation;

namespace test2
{
    public interface IComputer
    {
        string GetDescription();
        float GetPrice();
    }
    public class DefaultComputerSet1 : IComputer {


        public string GetDescription()
        {
            return "Default computer set 1";
        }

        public float GetPrice()
        {
            return 30000f;
        }
    }

    public abstract class ComputerUpgrade : IComputer
    {
        private readonly IComputer _computer;
        public ComputerUpgrade(IComputer computer)
        {
            _computer = computer;
        }

        public virtual string GetDescription()
        {
            return _computer.GetDescription();
        }

        public virtual float GetPrice()
        {
            return _computer.GetPrice();
        }
    }

    public class GeforceRTX2080 : ComputerUpgrade{

        public GeforceRTX2080(IComputer computer) : base(computer)
        {
            
        }

        public override string GetDescription()
        {
            return base.GetDescription() + " + Geforce RTX 2080";
        }

        public override float GetPrice()
        {
            return base.GetPrice() + 47900f;
        }
    }

    public class CreativeSoundAE7 : ComputerUpgrade
    {
        public CreativeSoundAE7(IComputer computer) : base(computer)
        {
        }

        public override string GetDescription()
        {
            return base.GetDescription() + " + Creative Sound Blaster AE7";
        }

        public override float GetPrice()
        {
            return base.GetPrice() + 6000f;
        }
    }

    public partial class ViewController : NSViewController
    {
        public ViewController(IntPtr handle) : base(handle)
        {
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();


            // Do any additional setup after loading the view.
        }

        partial void ClickedButton(NSObject sender)
        {
           
            DefaultComputerSet1 basicComputer = new DefaultComputerSet1();
            ComputerUpgrade upgradeSet = new GeforceRTX2080(basicComputer);
            upgradeSet = new CreativeSoundAE7(upgradeSet);


            Console.WriteLine("Description : " + upgradeSet.GetDescription());
            Console.WriteLine("Price : " + upgradeSet.GetPrice());
        }


        public override NSObject RepresentedObject
        {
            get
            {
                return base.RepresentedObject;
            }
            set
            {
                base.RepresentedObject = value;
                // Update the view, if already loaded.
            }
        }
    }
}