设计模式之☞简单工厂模式

通过多态制作一个简单的计算器

Operation类：

   public class Operation
    {
        private double _numberA = 0;
        private double _numberB = 0;
        public double NumberA
        {
            get
            {
                return _numberA;
            }

            set
            {
                _numberA = value;
            }
        }
        public double NumberB
        {
            get
            {
                return _numberB;
            }

            set
            {
                _numberB = value;
            }
        }
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }

简单工厂类：

public class OperationFactory
    {
        public static Operation createOperate(string operate)
        {
            Operation oper = null;
            switch (operate)
            {
                case "+":
                    oper = new OperationAdd();
                    break;
                case "-":
                    oper = new OperationSub();
                    break;
                case "*":
                    oper = new OperationMul();
                    break;
                case "/":
                    oper = new OperationDiv();
                    break;
            }
            return oper;
        }
    }

加法类，继承Operation：

class OperationAdd:Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA + NumberB;
            return result;
        }
    }

减法类，继承Operation：

    class OperationSub:Operation
    {
        public override double GetResult()
        {
            double result = 0;
            result = NumberA - NumberB;
            return result;
        }
    }

乘法类，继承Operation：

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

除法类，继承Operation：

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

调用：

        private void button1_Click(object sender, EventArgs e)
        {
            Operation oper = OperationFactory.createOperate(textBox4.Text);
            oper.NumberA =Convert.ToDouble(textBox1.Text);
            oper.NumberB = Convert.ToDouble(textBox2.Text);
            textBox3.Text = oper.GetResult().ToString();
        }