先看下代码，最后再看效果，代码如下：

using System;using System.Collections.Generic;using System.ComponentModel;using System.Data;using System.Drawing;using System.Drawing.Drawing2D;using System.IO;using System.Linq;using System.Text;using System.Threading.Tasks;using System.Windows.Forms;namespace winform验证码{ public partial class Form1 : Form { public Form1() { InitializeComponent(); } //-------------这个就是最后的验证码的结果------------- string ther = null; void getyzm() { //初始化验证码 MYYZM yzm = new MYYZM(0, MYYZM.CodeType.Romdom, false); //生成显示验证码图像 pictureBox1.Image = Bitmap.FromStream(yzm.CreateCheckCodeImage(out ther)); } private void Form1_Load(object sender, EventArgs e) { //1、窗体启动时产生验证码 getyzm(); } private void pictureBox1_Click(object sender, EventArgs e) { //2、点击验证码时更换 getyzm(); } private void button1_Click(object sender, EventArgs e) { //3、判断验证码正误 string inputstr = textBox1.Text; if(inputstr.Equals(ther)) { MessageBox.Show('正确！'); } else { MessageBox.Show('错误！'); } } public class MYYZM { #region 私有字段 private const double PI = 3; private const double PI2 = 6; //验证码区分大小写 private bool _qfdxx; //验证码字符数量 private int _len; //验证码类型 private CodeType _codetype; private readonly Single _jianju = (float)18.0; private readonly Single _height = (float)24.0; private string _checkCode; private string _checkResult; //左空隙 private int leftspace = 10; #endregion #region 属性 public string MYYZMcode { get { return _checkCode; } } #endregion #region 构造函数 /// <summary> /// public constructors /// </summary> /// <param name='len'> 验证码长度 </param> /// <param name='ctype'> 验证码类型：字母、数字、字母 数字、算数 </param> public MYYZM(int len, CodeType ctype, bool qfdxx) { _qfdxx = qfdxx; Random random = new Random(); if (len == 0) { _len = random.Next(4, 7); } else { this._len = len; } if (ctype == CodeType.Romdom) { int n = random.Next(1, 6); switch (n) { case 1: this._codetype = CodeType.Alphas; break; case 2: this._codetype = CodeType.Characters; break; case 3: this._codetype = CodeType.Numbers; break; case 4: this._codetype = CodeType.Words; break; case 5: this._codetype = CodeType.SuanShu; break; default: this._codetype = CodeType.Alphas; break; } } else { this._codetype = ctype; } } #endregion #region 共有变量 /// <summary> /// ?验证码类型：字母、数字、字母 数字 /// </summary> public enum CodeType { Romdom, Words, Numbers, Characters, Alphas, SuanShu } #endregion #region 私有方法 private string GenerateNumbers() { string strOut = ''; System.Random random = new Random(); for (int i = 0; i < _len; i ) { string num = Convert.ToString(random.Next(10000) % 10); strOut = num; } return strOut.Trim(); } private string GenerateCharacters() { string strOut = ''; System.Random random = new Random(); for (int i = 0; i < _len; i ) { string num = Convert.ToString((char)(65 random.Next(10000) % 26)); strOut = num; } return strOut.Trim(); } // private string GenerateAlphas() { string strOut = ''; string num = ''; System.Random random = new Random(); for (int i = 0; i < _len; i ) { if (random.Next(500) % 2 == 0) { num = Convert.ToString(random.Next(10000) % 10); } else { num = Convert.ToString((char)(65 random.Next(10000) % 26)); } strOut = num; } return strOut.Trim(); } private string GenerateSuanShu() { string strOut = ''; System.Random random = new Random(); int a = random.Next(1, 10); int b = random.Next(1, 10); if (a < b) { int t = a; a = b; ; b = t; } string fh = ' '; int jiajian = random.Next(1, 3); if (jiajian == 1) { fh = '-'; _checkResult = (a - b).ToString(); } else { fh = ' '; _checkResult = (a b).ToString(); } strOut = a fh b; return strOut.Trim(); } private System.Drawing.Bitmap TwistImage(Bitmap srcBmp, bool bXDir, double dMultValue, double dPhase) { System.Drawing.Bitmap destBmp = new Bitmap(srcBmp.Width, srcBmp.Height); // 将位图背景填充为白色 System.Drawing.Graphics graph = System.Drawing.Graphics.FromImage(destBmp); graph.FillRectangle(new SolidBrush(System.Drawing.Color.White), 0, 0, destBmp.Width, destBmp.Height); graph.Dispose(); double dBaseAxisLen = bXDir ? (double)destBmp.Height : (double)destBmp.Width; for (int i = 0; i < destBmp.Width; i ) { for (int j = 0; j < destBmp.Height; j ) { double dx = 0; dx = bXDir ? (PI2 * (double)j) / dBaseAxisLen : (PI2 * (double)i) / dBaseAxisLen; dx = dPhase; double dy = Math.Sin(dx); // 取得当前点的颜色 int nOldX = 0, nOldY = 0; nOldX = bXDir ? i (int)(dy * dMultValue) : i; nOldY = bXDir ? j : j (int)(dy * dMultValue); System.Drawing.Color color = srcBmp.GetPixel(i, j); if (nOldX >= 0 && nOldX < destBmp.Width && nOldY >= 0 && nOldY < destBmp.Height) { destBmp.SetPixel(nOldX, nOldY, color); } } } return destBmp; } #endregion #region 共有方法 /// <summary> /// 产生验证码的方法 /// </summary> /// <returns></returns> public Stream CreateCheckCodeImage(out string MYYZMCode) { string checkCode; switch (_codetype) { case CodeType.Alphas: checkCode = GenerateAlphas(); break; case CodeType.Numbers: checkCode = GenerateNumbers(); break; case CodeType.Characters: checkCode = GenerateCharacters(); break; case CodeType.SuanShu: checkCode = GenerateSuanShu(); break; default: checkCode = GenerateAlphas(); break; } if (_codetype == CodeType.SuanShu) { _checkCode = _checkResult; } else { _checkCode = checkCode; } if (_qfdxx) //区分大小写 { MYYZMCode = _checkCode; } else { _checkCode = _checkCode.ToLower(); MYYZMCode = _checkCode.ToLower(); } MemoryStream ms = null; // if (checkCode == null || checkCode.Trim() == String.Empty) return null; Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * _jianju) leftspace leftspace), (int)_height); Graphics g = Graphics.FromImage(image); try { Random random = new Random(); g.Clear(Color.Yellow); // 画图片的背景噪音线 for (int i = 0; i < 18; i ) { int x1 = random.Next(image.Width); int x2 = random.Next(image.Width); int y1 = random.Next(image.Height); int y2 = random.Next(image.Height); g.DrawLine(new Pen(Color.FromArgb(random.Next()), 1), x1, y1, x2, y2); } Font font = new System.Drawing.Font('Times New Roman', 15, System.Drawing.FontStyle.Bold); LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width leftspace, image.Height), Color.Black, Color.DarkRed, 1.2f, true); if (_codetype != CodeType.Words) { for (int i = 0; i < checkCode.Length; i ) { g.DrawString(checkCode.Substring(i, 1), font, brush, (2 i * _jianju) leftspace, 1); } } else { g.DrawString(checkCode, font, brush, 2, 2); } // 画图片的前景噪音点 for (int i = 0; i < 150; i ) { int x = random.Next(image.Width); int y = random.Next(image.Height); image.SetPixel(x, y, Color.FromArgb(random.Next())); } // 画图片的波形滤镜效果 if (_codetype != CodeType.Words) { image = TwistImage(image, true, 3, 1); } // 画图片的边框线 g.DrawRectangle(new Pen(Color.Green), 0, 0, image.Width - 1, image.Height - 1); ms = new System.IO.MemoryStream(); image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif); } finally { g.Dispose(); image.Dispose(); } return ms; } #endregion } }}
说明：

getyzm();就是产生及刷新验证码的方法
用用户输入与 ther 对比来判断验证码是否正确。
效果如下：

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