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：
1 /// <summary>
2 /// 生成验证码对象
3 /// </summary>
4 public class ValidateCode
5 {
6 public ValidateCode()
7 {
8 }
9 ///<summary>
10 /// 验证码的最大长度
11 ///</summary>
12 public int MaxLength
13 {
14 get { return 10; }
15 }
16 ///<summary>
17 /// 验证码的最小长度
18 ///</summary>
19 public int MinLength
20 {
21 get { return 1; }
22 }
23 ///<summary>
24 /// 生成验证码
25 ///</summary>
26 ///<param name="length">指定验证码的长度</param>
27 ///<returns></returns>
28 public string CreateValidateCode(int length)
29 {
30 int[] randMembers = new int[length];
31 int[] validateNums = new int[length];
32 string validateNumberStr = "";
33 //生成起始序列值
34 int seekSeek = unchecked((int)DateTime.Now.Ticks);
35 Random seekRand = new Random(seekSeek);
36 int beginSeek = (int)seekRand.Next(0, Int32.MaxValue - length * 10000);
37 int[] seeks = new int[length];
38 for (int i = 0; i < length; i++)
39 {
40 beginSeek += 10000;
41 seeks[i] = beginSeek;
42 }
43 //生成随机数字
44 for (int i = 0; i < length; i++)
45 {
46 Random rand = new Random(seeks[i]);
47 int pownum = 1 * (int)Math.Pow(10, length);
48 randMembers[i] = rand.Next(pownum, Int32.MaxValue);
49 }
50 //抽取随机数字
51 for (int i = 0; i < length; i++)
52 {
53 string numStr = randMembers[i].ToString();
54 int numLength = numStr.Length;
55 Random rand = new Random();
56 int numPosition = rand.Next(0, numLength - 1);
57 validateNums[i] = Int32.Parse(numStr.Substring(numPosition, 1));
58 }
59 //生成验证码
60 for (int i = 0; i < length; i++)
61 {
62 validateNumberStr += validateNums[i].ToString();
63 }
64 return validateNumberStr;
65 }
66 ///<summary>
67 /// 创建验证码的图片
68 ///</summary>
69 ///<param name="containsPage">要输出到的page对象</param>
70 ///<param name="validateNum">验证码</param>
71 public byte[] CreateValidateGraphic(string validateCode)
72 {
73 Bitmap image = new Bitmap((int)Math.Ceiling(validateCode.Length * 14.0), 22);
74 Graphics g = Graphics.FromImage(image);
75 try
76 {
77 //生成随机生成器
78 Random random = new Random();
79 //清空图片背景色
80 g.Clear(Color.White);
81 //画图片的干扰线
82 for (int i = 0; i < 25; i++)
83 {
84 int x1 = random.Next(image.Width);
85 int x2 = random.Next(image.Width);
86 int y1 = random.Next(image.Height);
87 int y2 = random.Next(image.Height);
88 g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
89 }
90 Font font = new Font("Arial", 14, (FontStyle.Bold | FontStyle.Italic));
91 LinearGradientBrush brush = new LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height),
92 Color.Blue, Color.DarkRed, 1.5f, true);
93 g.DrawString(validateCode, font, brush, 3, 2);
94 //画图片的前景干扰点
95 for (int i = 0; i < 100; i++)
96 {
97 int x = random.Next(image.Width);
98 int y = random.Next(image.Height);
99 image.SetPixel(x, y, Color.FromArgb(random.Next()));
100 }
101 //画图片的边框线
102 g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);
103 //保存图片数据
104 MemoryStream stream = new MemoryStream();
105 image.Save(stream, ImageFormat.Jpeg);
106 //输出图片流
107 return stream.ToArray();
108 }
109 finally
110 {
111 g.Dispose();
112 image.Dispose();
113 }
114 }
115
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
1 /// <summary>
2 /// 生成验证码图像对象
3 /// </summary>
4 /// <returns></returns>
5 public ActionResult GetValidateCode()
6 {
7 ValidateCode vCode = new ValidateCode();
8 string code = vCode.CreateValidateCode(4);
9 Session["ValidateCode"] = code;
10 byte[] bytes = vCode.CreateValidateGraphic(code);
11 return File(bytes, @"image/jpeg");
12
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
1 /// <summary>
2 /// 得到当前验证码
3 /// </summary>
4 /// <returns></returns>
5 public ActionResult GetCurrentValidateCode()
6 {
7 return Content(Session["ValidateCode"].ToString());
8
最后，就是页面上的事了，看代码：
1 <div id="ValidateCodeSpan">
2 请输入验证码：@Html.TextBox("VCode")
3 <img id="valiCode" style="cursor: pointer;" src="/Common/GetValidateCode" alt="看不清？请点我" />
4 @Html.Hidden("ValidateCode")
5 <script type="text/javascript">
6 $(function () {
7 //首次加载
8 $("#valiCode").attr("src","/Common/GetValidateCode?time=" + (new Date()).getTime());
9 $.get("/Common/GetCurrentValidateCode", function (data) {
10 $("#ValidateCode").val(data);
11 });
12 //单击验证码事件
13 $("#valiCode").bind("click", function () {
14 this.src = "/Common/GetValidateCode?time=" + (new Date()).getTime();
15 $.get("/Common/GetCurrentValidateCode", function (data) {
16 $("#ValidateCode").val(data);
17 });
18 });
19 });
20 </script>
21
作者：仓储大叔，张占岭，
荣誉：微软MVP
