转：http://www.cnblogs.com/liuxiaoji/p/4920382.html
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：
/// <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 byte[] 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 return stream.ToArray(); } finally { g.Dispose(); image.Dispose(); } }
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" 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>