ASP.NET MVC3实现无刷新验证码

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>