封装计算方法实现面向对象计算器。

 public abstract class calculator
    {
        public double number1 { get; set; }
        public double number2 { get; set; }
        public abstract double calculate();
    }

class add : calculator
    {
        public add(double n1,double n2)
        {
            this.number1 = n1;
            this.number2 = n2;
        }
        public override double calculate()
        {
            return number1 + number2;
        }
    }

class sub : calculator
    {
        public sub(double n1,double n2 )
        {
            this.number1 = n1;
            this.number2 = n2;
        }

        public override double calculate()
        {

            return number1 - number2;
        }
    }

 

class program
    {
        static void main(string[] args)
        {
            console.writeline("第一个数");
            double number1 = convert.todouble(console.readline());
            console.writeline("操作符");
            string  operate= console.readline();
            console.writeline("第二个数");
            double number2= convert.todouble(console.readline());
            calculator calculator = null;
            switch (operate)
            {
                case "+":
                    calculator = new add(number1, number2); 
                    break;
                case "-":
                    calculator = new sub(number1, number2);
                    break;
            }
            if (calculator!=null)
            {
                console.writeline("结果是：{0}",calculator.calculate());
            }
            else
            {
                console.writeline("没有这种操作");
            }
        }
    }

优化：

 calculator calculator = getcomputeobject(operate, number1, number2);

 private static calculator getcomputeobject(string perate, double number1, double number2)
        {
            calculator result = null;
            switch (perate)
            {
                case "+":
                    result = new add(number1, number2);
                    break;
                case "-":
                    result = new sub(number1, number2);
                    break;
            }
            return result;
        }