public virtual void calc()
Console.WriteLine("Base Calculate method");
public class Addition : Calculator
public override void calc()
Console.WriteLine("The addition result is " + c);
public class Subtraction : Calculator
public override void calc()
Console.WriteLine("The subtraction result is " + c);
public static void Main()
Calculator calcBase = new Calculator();
Addition a = new Addition();
Subtraction b = new Subtraction();