ASP.NET MVC3实现无刷新验证码

首先，在公用项目中建立一个生成图片验证码的类型ValidateCode，代码如下

/// <summary>

   /// 生成验证码对象

   /// </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 byte[] CreateValidateGraphic(string validateCode)

     {

       Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 14.0), 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", 14, (FontStyle.Bold | FontStyle.Italic));

         LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height),

         Color.Blue, Color.DarkRed, 1.5f, 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();

       }

     }

   }

然后，在当前公用的controller中添加一个返回文件类型的action,当然也可以是所有返回类型的基类ActionResult，这个方法用来返回一个图像对象

/// <summary>

     /// 生成验证码图像对象

     /// </summary>

     /// <returns></returns>

     public ActionResult GetValidateCode()

     {

       ValidateCode vCode = new ValidateCode();

       string code = vCode.CreateValidateCode(4);

       Session["ValidateCode"] = code;

       byte[] bytes = vCode.CreateValidateGraphic(code);

       return File(bytes, @"image/jpeg");

     }

再次，需要我们写一个返回当前验证吗的方法，这是作无刷新验证码的关键

/// <summary>

     /// 得到当前验证码

     /// </summary>

     /// <returns></returns>

     public ActionResult GetCurrentValidateCode()

     {

       return Content(Session["ValidateCode"].ToString());

     }

最后，就是页面上的事了，看代码

<div id="ValidateCodeSpan">

                     请输入验证码：@Html.TextBox("VCode")

                     <img id="valiCode" style="cursor: pointer;" src="/Common/GetValidateCode" alt="看不清？请点我" />

                     @Html.Hidden("ValidateCode")

                     <script type="text/javascript">

                         $(function () {

                             //首次加载

                             $("#valiCode").attr("src","/Common/GetValidateCode?time=" + (new Date()).getTime());

                             $.get("/Common/GetCurrentValidateCode", function (data) {

                                 $("#ValidateCode").val(data);

                             });

                             //单击验证码事件

                             $("#valiCode").bind("click", function () {

                                 this.src = "/Common/GetValidateCode?time=" + (new Date()).getTime();

                                 $.get("/Common/GetCurrentValidateCode", function (data) {

                                     $("#ValidateCode").val(data);

                                 });

                             });

                         });

                     </script>

                 </div>