C#写简单的计算器

 Form1.cs  代码如下：

using System;
using System.Windows.Forms;
namespace WindowsCal
{

    public partial class Form1 : Form
    {       

        public string Operator;
        public double Result;
        public bool isFirstNum;
        public Form1()
        {
            InitializeComponent();
            isFirstNum = false;
        }      

        private void btnNumber_Click(object sender, EventArgs e)
        {
            
            if(this.txtNumber.Text == "0")
            {
                this.txtNumber.Text = "";
            }
            Button btn = sender as Button;
            if (isFirstNum)
            {
                this.txtNumber.Text = btn.Text;
                isFirstNum = false;
            }
            else
                this.txtNumber.Text += btn.Text;
           
        }

        private void btnDel_Click(object sender, EventArgs e)
        {
            if (this.txtNumber.Text == "0") return;
            string res = this.txtNumber.Text;
            if (res.Length != 1)
                this.txtNumber.Text = res.Substring(0, res.Length - 1);
            else
                this.txtNumber.Text = "0";
           
        }

        private void btnEqu_Click(object sender, EventArgs e)
        {
            //if (this.txtNumber.Text == "0") return;
            double number = Convert.ToDouble(this.txtNumber.Text);
            switch(Operator)
            {
                case "+":
                    Result += number;
                    break;
                case "-":
                    Result -= number;
                    break;
                case "×":
                    Result *= number;
                    break;
                case "÷":
                    if (number == 0)
                    {
                        txtNumber.Text = "除数不能为0";
                        isFirstNum = true;
                        return;
                    }
                    else
                    {
                        Result /= number;
                    }                    
                    break;
                default:
                    Result = number;
                    break;
            }
            this.txtNumber.Text = Result.ToString();
            isFirstNum = true;
            Operator = "";
        }

        private void btnOperator_Click(object sender, EventArgs e)
        {
            Button btn = sender as Button;
            Operator = btn.Text;
            //if (this.txtNumber.Text == "0")
            //    return;
            Result = Convert.ToDouble(this.txtNumber.Text);
            isFirstNum = true;
        }

        private void btnZero_Click(object sender, EventArgs e)
        {
            this.txtNumber.Text = "0";
        }

        private void btnDot_Click(object sender, EventArgs e)
        {
            if (this.txtNumber.Text.IndexOf('.') == -1)
                this.txtNumber.Text += ".";
            else
                return;
        }
    }
}

开发界面写起来挺简单的。

界面如下：