using System;

​

interface IPrinter

{

    void Print();

}

public class PrinterOne : IPrinter

{

    public virtual void Print() 

    {

        Console.WriteLine("PrinterOne.");

    }

}

​

public class PrinterTwo : PrinterOne

{

    public virtual new void Print()

    //public override void Print()

    {

        Console.WriteLine("PrinterTwo.");

    }

}

​

public class PrinterThree : PrinterTwo

{

    public override void Print()

    {

        Console.WriteLine("PrinterThree.");

    }

}

​

public class PrinterFour : PrinterThree

{

    public override void Print()

    {

        Console.WriteLine("PrinterFour.");

    }

}

​

​

public class Program

{

    public static void Main(string[] args)

    {

        IPrinter iprinter = new PrinterFour();

        iprinter.Print();//the output is PrinterOne? why???

        //Console.ReadLine();

    }

​

}