static System.Security.Cryptography.RandomNumberGenerator RandomNumberGenerator = null;



        /// <summary>

        /// 回傳大於等於 0 小於 1

        /// </summary>

        /// <returns></returns>

        public static double NextDouble()

        {

            if (RandomNumberGenerator == null || LastRandomGenerateTime < DateTime.Now.AddMinutes(-1))

            {

                RandomNumberGenerator = System.Security.Cryptography.RandomNumberGenerator.Create();

            }



            // Generate four random bytes

            byte[] four_bytes = new byte[4];

            RandomNumberGenerator.GetBytes(four_bytes);



            // Convert the bytes to a UInt32

            uint scale = BitConverter.ToUInt32(four_bytes, 0);



            // And use that to pick a random number >= min and < max

            // 0 <= (scale / (uint.MaxValue + 1.0)) < 1

            return scale / (uint.MaxValue + 1.0);

        }



        /// <summary>

        /// 回傳值介於 min ~ (max - 1)

        /// </summary>

        /// <param name="min"></param>

        /// <param name="max"></param>

        /// <returns></returns>

        public static int GetRandomInt(int min, int max)

        {

            if(max < min)

            {

                throw new Exception("最大值不可小於最小值");

            }



            // Generate four random bytes

            byte[] four_bytes = new byte[4];

            RandomNumberGenerator.GetBytes(four_bytes);



            // And use that to pick a random number >= min and < max

            return (int)(min + (max - min) * NextDouble()); //因為 NextDouble 會小於 1，所以用無條件捨去.

        }



        /// <summary>

        /// 產生 0 ~ (max - 1) 的亂數

        /// </summary>

        /// <param name="max"></param>

        /// <returns></returns>

        public static int GetRandomInt(int max)

        {

            return GetRandomInt(0, max);

        }



        /// <summary>

        /// 產生 0 ~ (int.MaxValue - 1) 的亂數

        /// </summary>

        /// <returns></returns>

        public static int GetRandomInt()

        {

            return GetRandomInt(int.MaxValue);

        }