(深入.Net平台和C#编程)第六章.上机练习4.20170410

---------------------------------------------------父类---------------------------------------------------

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

namespace Calc.entity
{
    public class Op
    {
        public double No1 { get; set; }
        public double No2 { get; set; }
        public virtual double GetResult()
        {
            double result = 0;
            return result;
        }
    }
}

---------------------------------------------------子类(加)---------------------------------------------------

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

namespace Calc.entity
{
    public class Jia :Op
    {

        public override double GetResult()
        {
            double result = base.No1 + base.No2;
            return result;
        }
    }
}

---------------------------------------------------子类(减)---------------------------------------------------

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

namespace Calc.entity
{
    public class Jian:Op
    {
        public override double GetResult()
        {
            double result = base.No1 - base.No2;
            return result;
        }
    }
}

---------------------------------------------------子类(乘)---------------------------------------------------

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

namespace Calc.entity
{
    public class Cheng:Op
    {
        public override double GetResult()
        {
            double result = base.No1 * base.No2;
            return result;
        }
    }
}

---------------------------------------------------子类(除)---------------------------------------------------

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

namespace Calc.entity
{
    public class Chu : Op
    {
        public override double GetResult()
        {
            double result = base.No1 / base.No2;
            return result;
        }
    }
}

---------------------------------------------------窗体类---------------------------------------------------

using Calc.entity;
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace Calc
{
    public partial class frmCalc : Form
    {
        public frmCalc()
        {
            InitializeComponent();
        }

        private void btnCalc_Click(object sender, EventArgs e)
        {
            Op op = new Op();
            if (cmbFu.Text.Equals("+"))
            {
                op = new Jia();
            }
            if (cmbFu.Text.Equals("-"))
            {
                op = new Jian();
            }
            if (cmbFu.Text.Equals("*"))
            {
                op = new Cheng();
            }
            if (cmbFu.Text.Equals("/"))
            {
                op = new Chu();
            }
            if (string.IsNullOrEmpty(txtNo1.Text.Trim()) || string.IsNullOrEmpty(txtNo2.Text.Trim()))
            {
                MessageBox.Show("不能为空！！！");
                return;
            }
            op.No1 = double.Parse(txtNo1.Text);
            op.No2 = double.Parse(txtNo2.Text);
            lblResult.Text = op.GetResult().ToString();
        }

        private void frmCalc_Load(object sender, EventArgs e)
        {
            cmbFu.Items.Add("+");
            cmbFu.Items.Add("-");
            cmbFu.Items.Add("*");
            cmbFu.Items.Add("/");
        }
    }
}