C#生成随机验证码代码分享

        {
            get { return this.image; }
        }
        #endregion

        #region 构造函数
        public YZMHelper()
        {
            HttpContext.Current.Response.Expires = 0;
            HttpContext.Current.Response.Buffer = true;
            HttpContext.Current.Response.ExpiresAbsolute = DateTime.Now.AddSeconds(-1);
            HttpContext.Current.Response.AddHeader("pragma", "no-cache");
            HttpContext.Current.Response.CacheControl = "no-cache";
            this.text = Rand.Number(4);
            CreateImage();
        }
        #endregion

        #region 私有方法
        /// <summary>
        /// 获得下一个随机数
        /// </summary>
        /// <param name="max">最大值</param>
        private static int Next(int max)
        {
            rand.GetBytes(randb);
            int value = BitConverter.ToInt32(randb, 0);
            value = value % (max + 1);
            if (value < 0) value = -value;
            return value;
        }

        /// <summary>
        /// 获得下一个随机数
        /// </summary>
        /// <param name="min">最小值</param>
        /// <param name="max">最大值</param>