一、功能界面

图1 验证码(区分大小写)

图2 验证码(不区分大小写)

二、创建一个产生验证码的类Class1

（1）生成随机验证码字符串，用的是Random随机函数
（2）创建验证码图片，将该字符串画在PictureBox控件中

Class1.cs：

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Drawing;//图片using System.Windows.Forms;namespace ValidCodeTest{ public class Class1 { #region 验证码功能 /// <summary> /// 生成随机验证码字符串 /// </summary> public static string CreateRandomCode(int CodeLength) { int rand; char code; string randomCode = String.Empty;//随机验证码 //生成一定长度的随机验证码 //Random random = new Random();//生成随机数对象 for (int i = 0; i < CodeLength; i++) { //利用GUID生成6位随机数 byte[] buffer = Guid.NewGuid().ToByteArray();//生成字节数组 int seed = BitConverter.ToInt32(buffer, 0);//利用BitConvert方法把字节数组转换为整数 Random random = new Random(seed);//以生成的整数作为随机种子 rand = random.Next(); //rand = random.Next(); if (rand % 3 == 1) { code = (char)('A' + (char)(rand % 26)); } else if (rand % 3 == 2) { code = (char)('a' + (char)(rand % 26)); } else { code = (char)('0' + (char)(rand % 10)); } randomCode += code.ToString(); } return randomCode; } /// <summary> /// 创建验证码图片 /// </summary> public static void CreateImage(string strValidCode, PictureBox pbox) { try { int RandAngle = 45;//随机转动角度 int MapWidth = (int)(strValidCode.Length * 21); Bitmap map = new Bitmap(MapWidth, 28);//验证码图片—长和宽 //创建绘图对象Graphics Graphics graph = Graphics.FromImage(map); graph.Clear(Color.AliceBlue);//清除绘画面,填充背景色 graph.DrawRectangle(new Pen(Color.Black, 0), 0, 0, map.Width - 1, map.Height - 1);//画一个边框 graph.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias;//模式 Random rand = new Random(); //背景噪点生成 Pen blackPen = new Pen(Color.LightGray, 0); for (int i = 0; i < 50; i++) { int x = rand.Next(0, map.Width); int y = rand.Next(0, map.Height); graph.DrawRectangle(blackPen, x, y, 1, 1); } //验证码旋转，防止机器识别 char[] chars = strValidCode.ToCharArray();//拆散字符串成单字符数组 //文字居中 StringFormat format = new StringFormat(StringFormatFlags.NoClip); format.Alignment = StringAlignment.Center; format.LineAlignment = StringAlignment.Center; //定义颜色 Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple }; //定义字体 string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" }; for (int i = 0; i < chars.Length; i++) { int cindex = rand.Next(7); int findex = rand.Next(5); Font f = new System.Drawing.Font(font[findex], 13, System.Drawing.FontStyle.Bold);//字体样式(参数2为字体大小) Brush b = new System.Drawing.SolidBrush(c[cindex]); Point dot = new Point(16, 16); float angle = rand.Next(-RandAngle, RandAngle);//转动的度数 graph.TranslateTransform(dot.X, dot.Y);//移动光标到指定位置 graph.RotateTransform(angle); graph.DrawString(chars[i].ToString(), f, b, 1, 1, format); graph.RotateTransform(-angle);//转回去 graph.TranslateTransform(2, -dot.Y);//移动光标到指定位置 } pbox.Image = map; } catch (ArgumentException) { MessageBox.Show("验证码图片创建错误"); } } #endregion }}

三、调用

（1）更新验证码
（2）验证（区分大小写）
（3）验证（不区分大小写）

Form1.cs：

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;using ValidCodeTest;namespace ValidCode{ public partial class Form1 : Form { public Form1() { InitializeComponent(); } #region 验证码 private const int ValidCodeLength = 4;//验证码长度 private String strValidCode = "";//验证码 //调用自定义函数,更新验证码 private void UpdateValidCode() { strValidCode = Class1.CreateRandomCode(ValidCodeLength);//生成随机验证码 if (strValidCode == "") return; Class1.CreateImage(strValidCode, pbox1);//创建验证码图片 } #endregion private void pbox1_Click(object sender, EventArgs e) { UpdateValidCode();//点击更新验证码 } private void Form1_Load(object sender, EventArgs e) { UpdateValidCode();//加载更新验证码 } /// <summary> /// 验证（区分大小写） /// </summary> private void btn1_Click(object sender, EventArgs e) { string validcode = txtValidCode.Text.Trim(); char[] ch1 = validcode.ToCharArray(); char[] ch2 = strValidCode.ToCharArray(); int Count1 = 0;//字母个数 int Count2 = 0;//数字个数 if (String.IsNullOrEmpty(validcode) != true)//验证码不为空 { for (int i = 0; i < strValidCode.Length; i++) { if ((ch1[i] >= 'a' && ch1[i] <= 'z') || (ch1[i] >= 'A' && ch1[i] <= 'Z'))//字母 { if (ch1[i] == ch2[i]) { Count1++; } } else//数字 { if (ch1[i] == ch2[i]) { Count2++; } } } int CountSum = Count1 + Count2; if (CountSum == strValidCode.Length) { MessageBox.Show("验证通过", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); UpdateValidCode(); txtValidCode.Text = ""; txtValidCode.Focus(); } else { MessageBox.Show("验证失败", "警告", MessageBoxButtons.OK, MessageBoxIcon.Exclamation); UpdateValidCode();//更新验证码 txtValidCode.Text = ""; txtValidCode.Focus(); } } else//验证码为空 { MessageBox.Show("请输入验证码", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); UpdateValidCode();//更新验证码 txtValidCode.Text = ""; txtValidCode.Focus(); } } /// <summary> /// 验证（不区分大小写） /// </summary> private void btn2_Click(object sender, EventArgs e) { string validcode = txtValidCode.Text.Trim(); if (String.IsNullOrEmpty(validcode) != true)//验证码不为空 { if (validcode.ToLower() == strValidCode.ToLower()) { MessageBox.Show("验证通过", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); UpdateValidCode(); txtValidCode.Text = ""; txtValidCode.Focus(); } else { MessageBox.Show("验证失败", "警告", MessageBoxButtons.OK, MessageBoxIcon.Exclamation); UpdateValidCode();//更新验证码 txtValidCode.Text = ""; txtValidCode.Focus(); } } else//验证码为空 { MessageBox.Show("请输入验证码", "提示", MessageBoxButtons.OK, MessageBoxIcon.Information); UpdateValidCode();//更新验证码 txtValidCode.Text = ""; txtValidCode.Focus(); } } }}

.exe测试文件下载: ValidCode_jb51.zip

参考文章：
https:///p/d89f22cf51bf

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