using System;

public abstract class Template

{

    public string sender;

        protected Template(string sender) {

        // an abstract class cannot be instantiated by itself, so we have a protected

        // constructor

        this.sender = sender;

    }

    // abstract methods that a non-abstract derived class must implement

    protected abstract void PrintHeader(string recipient);

    protected abstract void PrintContent(string content);

    protected abstract void PrintFooter();

        // implementation

    public void Print(string recipient, string content)

    {

        Console.WriteLine("------------------------------------");

        PrintHeader(recipient);

        Console.WriteLine();

        PrintContent(content);

        Console.WriteLine();

        PrintFooter();

        Console.WriteLine("------------------------------------");

    }

}

public class Memo : Template

{

    public Memo(string sender) : base(sender) {

    }

    protected override void PrintHeader(string recipient)

    {

        Console.WriteLine("Dear {0},",recipient);

    }

    protected override void PrintContent(string content)

    {

        Console.WriteLine(content);

    }

    protected override void PrintFooter()

    {

        Console.WriteLine("From {0}",sender);

    }

}

​

​

public class Program

{

    public static void Main()

    {

        Template t = new Memo("Jane");

        t.Print("Peter","How are you?");

    }

}

​