使用asp.net mvc验证码类的方法技巧

namespace QJW.VerifyCode
{
 //用法：
 //public FileContentResult CreateValidate()
 //{
 // ValidateCode vCode = new ValidateCode();
 // string code = vCode.CreateValidateCode(5);
 // Session["ValidateCode"] = code;
 // byte[] bytes = vCode.CreateValidateGraphic(code);
 // return File(bytes, "image/JPEG");
 //}


 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 * 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();
   }
  }
  /// <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;
  }
 }
}

  public FileContentResult CreateValidate()
  {
   ValidateCode vCode = new ValidateCode();
   string code = vCode.CreateValidateCode(5);
   Session["ValidateCode"] = code;
   byte[] bytes = vCode.CreateValidateGraphic(code);

   return File(bytes, "image/JPEG");
  }

function reloadcode() {
  var verify = document.getElementById('safecode');
  verify.setAttribute('src', '/common/CreateValidate?' + Math.random());
 }