LSP1Before.cs

public class Bird 
{
  public virtual void Fly() 
  { Console.Write("Fly"); 
  }
}
public class Eagle : Bird 
{
  public override void Fly() 
  { Console.Write("Eagle Fly"); 
  }
}
public class Duck : Bird 
{
  public override void Fly() 
  { Console.Write("Duck Fly"); 
  }
}
public class Penguin : Bird 
{
  public override void Fly() 
  { throw new NoFlyException(); 
  }
}

var birds = new List { new Bird(), new Eagle(), new Duck(), new Penguin() };
foreach(var bird in birds) bird.Fly(); 
// Tới pengiun thì lỗi vì cánh cụt quăng Exception