public abstract class Rule
    {
        public abstract void replace();

    }

    public class RuleOne : Rule
    {
        public RuleOne()
        {
        }
        public override void replace()
        {
            System.Console.WriteLine("replace1");
        }

    }

    public class RuleTwo : Rule
    {
        public RuleTwo()
        {
        }

        public override void replace()
        {
            Console.WriteLine("replace2");
        }

    }

    public class RuleSolve 
    {
        private Rule strategy;

        public RuleSolve(Rule rule)
        {
            this.strategy = rule;
        }

        public void getContext()
        {
            this.strategy.replace();
        }
    }
    class SrategyTest
    {
        [STAThread]
        static void Main(string[] args)
        {
            
            RuleSolve solver = new RuleSolve(new RuleOne());
            solver.getContext();

            solver = new RuleSolve(new RuleTwo());
            solver.getContext();
        }
    }