namespace 策略模式
{
    //抽象算法类
    abstract class Operation
    {
        private double _leftNum;

        public double LeftNum
        {
            get { return _leftNum; }
            set { _leftNum = value; }
        }
        private double _rightNum;

        public double RightNum
        {
            get { return _rightNum; }
            set { _rightNum = value; }
        }

        public double GetResult();
    }

    //具体算法1 继承抽象算法类
    public class OperationAdd : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = LeftNum + RightNum;
            return result;
        }
    }

    public class OperationSub : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = LeftNum + RightNum;
            return result;
        }
    }

    public class OperationMul : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = LeftNum * RightNum;
            return result;
        }
    }

    public class OperationDiv : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            if (LeftNum == 0)
            {
                throw new Exception("除数不能为 0。");
            }
            result = LeftNum / RightNum;
            return result;
        }
    }

    public class OperationSqr : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = LeftNum * LeftNum;
            return result;
        }
    }

    public class OperationSqrt : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            if (LeftNum == 0)
            {
                throw new Exception("负数不能开平方根。");
            }
            result = Math.Sqrt(LeftNum);
            return result;
        }
    }

    public class OperationReverse : Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = -LeftNum;
            return result;
        }
    }

    //上下文，用来维护一个对 算法 的引用
    public class Context
    {
        Operation _op;

        public Context(Operation op)
        {
            _op = op;
        }

        public void ContextInterface()
        {
            _op.GetResult();
        }
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine(CalcByBinaryOperator<int>(4, 5, (x, y) => x + y));
            Console.WriteLine(CalcByBinaryOperator<float>(4.5f, 5f, (x, y) => x - y));
            Console.WriteLine(CalcByBinaryOperator<double>(4f, 0.5f, (x, y) => Math.Pow(x, y)));
        }

        static T CalcByBinaryOperator<T>(T left, T right, Func<T, T, T> Strategy)
        {
            return Strategy(left, right);
        }
    }
}