decorator_1.cs

using System;

namespace decorator_1
{
    class Program
    {
        static void Main(string[] args)
        {
            var msg = "I love C-sharp";
            var simpleMsg = new SimpleMessage(msg);
            var excitedDecoratedMsg = new ExcitedMessageDecorator(simpleMsg);
            var quizzicalDecoratedMsg = new QuizzicalMessageDecorator(simpleMsg);
            var excitedAndQuizzicalDecoratedMsg = new QuizzicalMessageDecorator(excitedDecoratedMsg);

            IMessage[] messages = { simpleMsg, excitedDecoratedMsg, 
                                    quizzicalDecoratedMsg, excitedAndQuizzicalDecoratedMsg };
            foreach (IMessage m in messages)
            {
                m.PrintMessage();
            }
                // I love C-sharp
                // I love C-sharp!!!
                // I love C-sharp???
                // I love C-sharp!!!???

            simpleMsg.PrintMessage();
                // I love C-sharp
        }
    }

    public interface IMessage
    {
        string GetMessage();

        void PrintMessage();
    }

    public class SimpleMessage : IMessage
    {
        private string Content;

        public SimpleMessage(string content)
        {
            this.Content = content;
        }

        public string GetMessage()
        {
            return this.Content;
        }

        public void PrintMessage()
        {
            Console.WriteLine(this.GetMessage());
        }
    }

    public abstract class MessageDecorator : IMessage
    {
        private IMessage Message;

        public MessageDecorator(IMessage message)
        {
            this.Message = message;
        }

        public virtual string GetMessage()
        {
            return this.Message.GetMessage();
        }

        public virtual void PrintMessage()
        {
            this.Message.PrintMessage();
        }
    }

    public class ExcitedMessageDecorator : MessageDecorator
    {
        public ExcitedMessageDecorator(IMessage message) : base(message) {}

        public override string GetMessage()
        {
            return base.GetMessage() + "!!!";
        }

        public override void PrintMessage()
        {
            Console.WriteLine(this.GetMessage());
        }
    }

    public class QuizzicalMessageDecorator : MessageDecorator
    {
        public QuizzicalMessageDecorator(IMessage message) : base(message) {}

        public override string GetMessage()
        {
            return base.GetMessage() + "???";
        }

        public override void PrintMessage()
        {
            Console.WriteLine(this.GetMessage());
        }
    }
}