MVC3 无刷新验证码

在MVC中进行留言，评论等功能时，不可避免会用到表单提交时的验证码问题，有时，我们的作法是，当表单被提交后，在controller里去判断验证码的正确与否，但我认为这种用户体验是很差的，今天正好有后时间，把这方法的东西总结一下：

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>