using System;

namespace TestDI

{

//===========================   

    public class Program

    {

        public static void Main()

        {

            var writer = new ConsoleWriter();

            var dispatcher = new MessageDispatcher(writer);

            dispatcher.SendMessage("Some message");

        }

    }

​

//===========================   

    public interface IWriter 

    {

        void Write(string message);

    }

    public class ConsoleWriter : IWriter

    {

        public void Write(string message) {

            Console.WriteLine("I'm ConsoleWriter. Printing message: '{0}'", message);

        }

    }

    public class MessageDispatcher {

        IWriter writer = null;

        public MessageDispatcher(IWriter writer)

        {

            this.writer = writer;

        }

        public void SendMessage(string message)

        {

            writer.Write(message);

        }

    }

}