Use of verification code class in asp.net mvc

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());
  }