使用C# MVC实现带旋转角度的验证码技术

///  <summary>
    ///  Chaos验证码
    ///  FileName                        :        VerifyCode.cs      
    ///  Verion                          :              0.20
    ///  Author                          :              zhouyu   http://max.cszi.com
    ///  Update                        :              2007-10-10 51aspx.com
    ///  Description            :              验证码随机旋转一定角度,可使用前景色,背景色效果不大就不用了
    ///  </summary>

    public class ValidateCode
    {
        private int _length = 4;                        //验证码长度
        private int _fontSize = 18;              //字体最大尺寸
        private int _border = 0;                      //边框，0时没有连框
        private Color _backgroundColor = Color.AliceBlue;      //背景色
        private Color _fontColor = Color.Blue;          //验证码色51aspx
        private int _rateNumber = 10;              //验证码中的数字出现机率  ，越大出现的数字机率越大
        private string _randomChars;              //随机生成的验证码
        private int _randomAngle = 40;              //随机码的旋转角度
        private string _fontFamily = "Verdana";        //字体
        private int _chaosNumber = 0;                //噪点数量  ,0  时不用
        private Random random = new Random();    //随机种子51aspx.com，公用
        public ValidateCode()
        {

        }
        ///  <summary>
        ///  重载一  ：噪点
        ///  </summary>
        ///  <param  name="chaosNumber"></param>

        public ValidateCode(int chaosNumber)
        {
            _chaosNumber = chaosNumber;
        }
        ///  <summary>
        ///  重载二：长度，噪点
        ///  </summary>
        ///  <param  name="length"></param>
        ///  <param  name="chaosNumber"></param>
        public ValidateCode(int length, int chaosNumber)
        {
            _length = length;
            _chaosNumber = chaosNumber;
        }
        ///  <summary>
        ///  重载三：长度，噪点，数字机率
        ///  </summary>
        ///  <param  name="length"></param>
        ///  <param  name="chaosNumber"></param>
        ///  <param  name="rate">越大，生成的随机码中数字占的比例越多</param>
        public ValidateCode(int length, int chaosNumber, int rate)
        {
            _length = length;
            _chaosNumber = chaosNumber;
            _rateNumber = rate;
        }

        #region  .Length  验证码长度(默认4个)
        public int Length
        {