效果图：
代码区：
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 WindowsFormsApplication2{ public partial class Form1 : Form { //存储上次点击了什么按钮，0代表什么都没点击，1代表点击了数字按钮，2代表点击了运算符 private int prev = 0; //存储计算的中间结果 private decimal zj = 0; //记录上次按的什么运算符 private string prevysf = "+"; public Form1() { InitializeComponent(); } //数字键按钮 private void button8_Click(object sender, EventArgs e) { //将事件源转换为按钮 Button btn = sender as Button; //替换（如果下面文本框内容为0或者上次点击了运算符） if (prev == 2 || txtbottom.Text == "0") { txtbottom.Text = btn.Text; } //追加（如果下面文本框内容不为0并且上次没有点击运算符） else { txtbottom.Text += btn.Text; } //点击了数字按钮 prev = 1; } //运算符按钮 private void button17_Click(object sender, EventArgs e) { Button btn = sender as Button; //上次按了数字 if (prev == 1) { txttop.Text += txtbottom.Text + btn.Text; switch (prevysf) { case "+": zj = zj + Convert.ToDecimal(txtbottom.Text); break; case "-": zj = zj - Convert.ToDecimal(txtbottom.Text); break; case "*": zj = zj * Convert.ToDecimal(txtbottom.Text); break; case "/": zj = zj / Convert.ToDecimal(txtbottom.Text); break; } txtbottom.Text = zj.ToString(); } //上次按了运算符 else { string s = txttop.Text; s = s.Substring(0, s.Length - 1); s = s + btn.Text; txttop.Text = s; } //点击了运算符 prev = 2; //记录下运算符 prevysf = btn.Text; } //清零按钮 private void button19_Click(object sender, EventArgs e) { txttop.Text = ""; txtbottom.Text = "0"; prev = 0; zj = 0; prevysf = "+"; } private void button20_Click(object sender, EventArgs e) { txtbottom.Text = "0"; } //等号按钮 private void button4_Click(object sender, EventArgs e) { Button btn = sender as Button; txttop.Text += txtbottom.Text + btn.Text; switch (prevysf) { case "+": zj = zj + Convert.ToDecimal(txtbottom.Text); break; case "-": zj = zj - Convert.ToDecimal(txtbottom.Text); break; case "*": zj = zj * Convert.ToDecimal(txtbottom.Text); break; case "/": zj = zj / Convert.ToDecimal(txtbottom.Text); break; } txtbottom.Text = zj.ToString(); txttop.Text = ""; zj = 0; } //点 private void button3_Click(object sender, EventArgs e) { txtbottom.Text += "."; } }}