code for my blog http://blog.gravypower.net/dependency-injection-an-attempt-to-explain/

House.cs

public class House
{
  public LivingRoom livingRoom;

  public void LivingRoom ()
  {
    ILcd lcd = new Video();
    livingRoom = new LivingRoom(lcd);
    livingRoom.EnterRoom();
  }
}

ILcd.cs

public interface ILcd
{
  void Show();
}

LivingRoom.cs

public class LivingRoom
{
  private ILcd lcd;
  public LivingRoom(ILcd lcd)
  {
    this.lcd = lcd;
  }
 
  public void EnterRoom()
  {
    lcd.Show();
  }
}

Painting.cs

public class Painting : ILcd
{
  public void Show()
  {
    //Display Painting
  }
}