Decorator 2

using System;
using System.Collections.Generic;

namespace Decorator
{
    public interface IWriter
    {
        void Write(string message);
    }

    public class ConsoleLogWriter : IWriter
    {
        public void Write(string message)
        {
            Console.WriteLine("ConsoleLogWriter:" + message);
        }
    }

    public class FileLogWriter : IWriter
    {
        public void Write(string message)
        {
            Console.WriteLine("FileLogWriter:" + message);
        }
    }

    public class ClientWriter : IWriter
    {
        private List<IWriter> _writers = new List<IWriter>();

        public void Add(IWriter writer)
        {
            if (!_writers.Contains(writer))
                _writers.Add(writer);
        }

        public void Remove(IWriter writer)
        {
            if (_writers.Contains(writer))
                _writers.Remove(writer);
        }

        public void Write(string message)
        {
            for (var i = 0; i < _writers.Count; i++)
            {
                _writers[i].Write(message);
            }
        }
    }

    class Program
    {
        public static bool UseConsole = true;
        public static bool UseFile = true;

        static void Main(string[] args)
        {
            var clientWriter = new ClientWriter();

            if (UseConsole)
                clientWriter.Add(new ConsoleLogWriter());

            if (UseFile)
                clientWriter.Add(new FileLogWriter());

            clientWriter.Write("message");

            Console.ReadKey();
        }
    }
}