一、功能需求分析：
- 实现简单的0—9这10个数之间的加减乘除；
- 实现正负号功能；
- 实现清除功能；
- 实现小数点运算；
- 实现删除功能。
二、详细实现过程：
1. A代表第一个输入的数字，b代表第二个输入的数字，布尔型c为判断条件，d代表运算符号。
2. 第一个要解决的问题：怎样让按钮上的数字在文本框上显示？
通过if--else语句把按钮上的数字赋给文本框语句如下：textBox1.Text += "某个数字";
注意事项：除数不能为0，设计判断代码提示出错：if (d == "/")
{
textBox1.Clear();
MessageBox.Show("除数不能为零", "错误提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
}
3.第二个要解决的问题：怎样实现加减乘除运算？
在=号按钮中写代码：switch (d)
{
case "+":
a = b + double.Parse(textBox1.Text); break;
case "-":
a = b - double.Parse(textBox1.Text); break;
case "*":
a = b * double.Parse(textBox1.Text); break;
case "/":
a = b / double.Parse(textBox1.Text); break;
}
textBox1.Text = a + "";
4.接下来就是各个功能按键的实现过程:
（1）清除按钮：textBox1 .Text ="";
（2）正负键按钮：if (textBox1.Text.IndexOf("-") == -1 && textBox1.Text.Length > 0)
{
String s = textBox1.Text;
textBox1.Text = "-" + s;
}
else
{
if (textBox1.Text.Length > 0)
{
String s = textBox1.Text.Substring(1);
textBox1.Text="+s" ;
}
}
（3）退格按钮：if (textBox1.Text.Length > 0)
{
textBox1.Text = textBox1.Text.Substring(0, textBox1.Text.Length - 1);
}
三、功能按钮的设计
“+”按键：字体设计：宋体, 12pt, style=Bold, Italic
颜色设计：Highlight（蓝色）
“-“按键：字体设计：宋体, 12pt, style=Bold, Italic
颜色设计：Fuchsia（红色）
“*”按键：字体设计：宋体, 12pt, style=Bold, Italic
颜色设计：Red
“/”按键：字体设计：宋体, 12pt, style=Bold, Italic
颜色设计：255, 128, 0（橘黄色）
“=”按键：字体设计：宋体, 14.25pt, style=Bold
颜色设计：Lime（翠绿）
“C“按键：字体设计：宋体, 15pt；颜色设计：Lime（翠绿）
” ±“按钮：字体设计：宋体, 12pt；颜色设计：Highlight
“←”按键：字体设计：宋体, 12pt；颜色设计：Gold（金黄色）。
四、简易计算器展示：
源程序：
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 Calculator
{
public partial class Calculator : Form
{
private double a = 0;
private double b = 0;
private bool c = false;
private string d;
public Calculator()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
}
private void button1_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "1";
}
private void button2_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "2";
}
private void button3_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "3";
}
private void button4_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "4";
}
private void button5_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "5";
}
private void button6_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "6";
}
private void button7_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "7";
}
private void button8_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "8";
}
private void button9_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "9";
}
//10按钮“0”键
private void button10_Click(object sender, EventArgs e)
{
if (c == true)
{
textBox1.Text = "";
c = false;
}
textBox1.Text += "0";
if (d == "/")
{
textBox1.Clear();
MessageBox.Show("除数不能为零", "错误提示", MessageBoxButtons.OK, MessageBoxIcon.Warning);
}
}
//11按钮小数点
private void button11_Click(object sender, EventArgs e)
{
if (textBox1.Text == "")
{
textBox1.Text = "0.";
}
else if (textBox1.Text.IndexOf(".") >= 0)
{
MessageBox.Show("已经添加小数点1！", "提示");
}
else
{
textBox1.Text += ".";
}
}
private void button12_Click(object sender, EventArgs e)
{
c = true;
b = double.Parse(textBox1.Text);
d = "+";
}
private void button13_Click(object sender, EventArgs e)
{
c = true;
b = double.Parse(textBox1.Text);
d = "-";
}
private void button14_Click(object sender, EventArgs e)
{
c = true;
b = double.Parse(textBox1.Text);
d = "*";
}
private void button15_Click(object sender, EventArgs e)
{
c = true;
b = double.Parse(textBox1.Text);
d = "/";
}
//16按钮等号键
private void button16_Click(object sender, EventArgs e)
{
switch (d)
{
case "+":
a = b + double.Parse(textBox1.Text); break;
case "-":
a = b - double.Parse(textBox1.Text); break;
case "*":
a = b * double.Parse(textBox1.Text); break;
case "/":
a = b / double.Parse(textBox1.Text); break;
}
textBox1.Text = a + "";
c = true;
}
//17按钮清零
private void button17_Click(object sender, EventArgs e)
{
textBox1 .Text ="";
}
//18按钮正负键
private void button18_Click(object sender, EventArgs e)
{
if (textBox1.Text.IndexOf("-") == -1 && textBox1.Text.Length > 0)
{
String s = textBox1.Text;
textBox1.Text = "-" + s;
}
else
{
if (textBox1.Text.Length > 0)
{
String s = textBox1.Text.Substring(1);
textBox1.Text="+s" ;
}
}
}
//19按钮退格键
private void button19_Click(object sender, EventArgs e)
{
if (textBox1.Text.Length > 0)
{
textBox1.Text = textBox1.Text.Substring(0, textBox1.Text.Length - 1);
}
}
}
}