网站添加验证码，主要为防止机器人程序批量注册，或对特定的注册用户用特定程序暴力破解方式，以进行不断的登录、灌水等危害网站的操作。验证码被广泛应用在注册、登录、留言等提交信息到服务器端处理的页面中。
在ASP.NET网站中应用验证码是很容易的，网上有很多的解决方案。最近在做一个OA项目，因系统采用的ASP.NET MVC框架，同样在登录页中需用到验证码，故需将原来在ASP.NET网站中使用的验证码移植到ASP.NET MVC中。
原ASP.NET网站用来生成验证码的类文件ValidateCode.cs：
using System;using System.Drawing;using System.Drawing.Imaging;using System.Web.UI;using System.Drawing.Drawing2D;using System.IO;namespace SeniOA.MVC{ ???/// <summary> ???/// 生成验证码的类 ???/// </summary> ???public class ValidateCode ???{ ???????public ValidateCode() ???????{ ???????} ???????/// <summary> ???????/// 验证码的最大长度 ???????/// </summary> ???????public int MaxLength ???????{ ???????????get { return 10; } ???????} ???????/// <summary> ???????/// 验证码的最小长度 ???????/// </summary> ???????public int MinLength ???????{ ???????????get { return 1; } ???????} ???????/// <summary> ???????/// 生成验证码 ???????/// </summary> ???????/// <param name="length">指定验证码的长度</param> ???????/// <returns></returns> ???????public string CreateValidateCode(int length) ???????{ ???????????int[] randMembers = new int[length]; ???????????int[] validateNums = new int[length]; ???????????string validateNumberStr = ""; ???????????//生成起始序列值 ???????????int seekSeek = unchecked((int)DateTime.Now.Ticks); ???????????Random seekRand = new Random(seekSeek); ???????????int beginSeek = (int)seekRand.Next(0, Int32.MaxValue - length * 10000); ???????????int[] seeks = new int[length]; ???????????for (int i = 0; i < length; i++) ???????????{ ???????????????beginSeek += 10000; ???????????????seeks[i] = beginSeek; ???????????} ???????????//生成随机数字 ???????????for (int i = 0; i < length; i++) ???????????{ ???????????????Random rand = new Random(seeks[i]); ???????????????int pownum = 1 * (int)Math.Pow(10, length); ???????????????randMembers[i] = rand.Next(pownum, Int32.MaxValue); ???????????} ???????????//抽取随机数字 ???????????for (int i = 0; i < length; i++) ???????????{ ???????????????string numStr = randMembers[i].ToString(); ???????????????int numLength = numStr.Length; ???????????????Random rand = new Random(); ???????????????int numPosition = rand.Next(0, numLength - 1); ???????????????validateNums[i] = Int32.Parse(numStr.Substring(numPosition, 1)); ???????????} ???????????//生成验证码 ???????????for (int i = 0; i < length; i++) ???????????{ ???????????????validateNumberStr += validateNums[i].ToString(); ???????????} ???????????return validateNumberStr; ???????} ???????/// <summary> ???????/// 创建验证码的图片 ???????/// </summary> ???????/// <param name="containsPage">要输出到的page对象</param> ???????/// <param name="validateNum">验证码</param> ???????public void CreateValidateGraphic(string validateCode) ???????{ ???????????Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 12.0), 22); ???????????Graphics g = Graphics.FromImage(image); ???????????try ???????????{ ???????????????//生成随机生成器 ???????????????Random random = new Random(); ???????????????//清空图片背景色 ???????????????g.Clear(Color.White); ???????????????//画图片的干扰线 ???????????????for (int i = 0; i < 25; 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.Silver), x1, y1, x2, y2); ???????????????} ???????????????Font font = new Font("Arial", 12, (FontStyle.Bold | FontStyle.Italic)); ???????????????LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), ????????????????Color.Blue, Color.DarkRed, 1.2f, true); ???????????????g.DrawString(validateCode, font, brush, 3, 2); ???????????????//画图片的前景干扰点 ???????????????for (int i = 0; i < 100; i++) ???????????????{ ???????????????????int x = random.Next(image.Width); ???????????????????int y = random.Next(image.Height); ???????????????????image.SetPixel(x, y, Color.FromArgb(random.Next())); ???????????????} ???????????????//画图片的边框线 ???????????????g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1); ???????????????//保存图片数据 ???????????????MemoryStream stream = new MemoryStream(); ???????????????image.Save(stream, ImageFormat.Jpeg); ???????????????//输出图片流 ???????????????containsPage.Response.Clear(); ???????????????containsPage.Response.ContentType = "image/jpeg"; ???????????????containsPage.Response.BinaryWrite(stream.ToArray()); ???????????} ???????????finally ???????????{ ???????????????g.Dispose(); ???????????????image.Dispose(); ???????????} ???????} ???????/// <summary> ???????/// 得到验证码图片的长度 ???????/// </summary> ???????/// <param name="validateNumLength">验证码的长度</param> ???????/// <returns></returns> ???????public static int GetImageWidth(int validateNumLength) ???????{ ???????????return (int)(validateNumLength * 12.0); ???????} ???????/// <summary> ???????/// 得到验证码的高度 ???????/// </summary> ???????/// <returns></returns> ???????public static double GetImageHeight() ???????{ ???????????return 22.5; ???????} ???}}为适合ASP.NET MVC框架，修改其输出图片流的方法CreateValidateGraphic为：
View Code
在Controller.cs中，添加Action，用来设置将生成的验证码存入Session，并输出验证码图片：
public ActionResult GetValidateCode(){ ???ValidateCode vCode = new ValidateCode(); ???string code = vCode.CreateValidateCode(5); ???Session["ValidateCode"] = code; ???byte[] bytes = vCode.CreateValidateGraphic(code); ???return File(bytes, @"image/jpeg");}调用方式为：在需要使用验证码的页面中，加入<img>标签：
<img id="valiCode" style="cursor: pointer;" src="../Account/GetValidateCode" alt="验证码" />
到于Account/Login这个Action中的处理，只需加入对Session中验证码的判断：
[AcceptVerbs(HttpVerbs.Post)]public ActionResult Login(string userName, string password, bool rememberMe, string returnUrl,string code){ ???if (Session["ValidateCode"].ToString() != code) ???{ ???????ModelState.AddModelError("code", "validate code is error"); ???????return View(); ???} ???//此处验证用户名、密码 ???if (!ValidateLogOn(userName, password)) ???{ ???????return View(); ???} ???//验证成功 ???FormsAuthentication.SetAuthCookie(userName, rememberMe); ???if (!String.IsNullOrEmpty(returnUrl)) ???{ ???????return Redirect(returnUrl); ???} ???else ???{ ???????return RedirectToAction("Index", "Home"); ???}}为实现登录页中，点击图片切换验证码，可以登录页中加入此JS代码实现刷新验证码：
<script type="text/javascript" src="http://www.cnblogs.com/Scripts/jquery-1.3.2-vsdoc.js"></script><script type="text/javascript"> ???$(function() { ???$("#valiCode").bind("click", function() { ???????this.src = "../Account/GetValidateCode?time=" + (new Date()).getTime(); ???????}); ???????//alert("good"); ???});</script>ASP.NET MVC实现网站验证码功能
原文地址：https://www.cnblogs.com/lzfsuifeng/p/9074412.html