C# Decorator pattern implementation

Decorator.cs

// C# decorator example where every concrete decorator needs to implement doConcrete() instead of remembering to call base.doit()
// based on this example: https://sourcemaking.com/design_patterns/decorator/java/1

using System;

namespace Project1
{
    class Program
    {
        public static void Main(string[] args)
        {
            ICommonInterface[] vars = { new X(new Core()), new Y(new X(new Core())), new Z(new Y(new X(new Core()))) };
            foreach (var item in vars)
            {
                item.doit();
                Console.Write("  ");
            }

            // ADX  ADXDY  ADXDYDZ
        }
    }

    public interface ICommonInterface
    {
        void doit();
    }

    public abstract class Decorator : ICommonInterface
    {
        private readonly ICommonInterface core;
        public Decorator(ICommonInterface core)
        {
            this.core = core;
        }

        public void doit()
        {
            core.doit();
            Console.Write("D");
            doConcrete();
        }

        protected abstract void doConcrete();
    }

    public class Core : ICommonInterface
    {
        public void doit()
        {
            Console.Write("A");
        }
    }

    public class X : Decorator
    {
        public X(ICommonInterface core) : base(core)
        {
        }

        protected override void doConcrete()
        {
            Console.Write("X");
        }
    }

    public class Y : Decorator
    {
        public Y(ICommonInterface core) : base(core)
        {
        }

        protected override void doConcrete()
        {
            Console.Write("Y");
        }
    }

    public class Z : Decorator
    {
        public Z(ICommonInterface core) : base(core)
        {
        }

        protected override void doConcrete()
        {
            Console.Write("Z");
        }
    }
}