用CSharp生成强密码

　　在很多场景下，我们需要一个强密码来保证可访问的数据或系统。如何检查你的密码安全级别，可以到Microsoft Online Safety – Using strong password这个网站。代码并不复杂，看下面片段代码：

        /// <summary>
        /// create another string which is a concatenation of all above
        /// </summary>
        private string allChars = alphaCaps + alphaLow + numerics + special;
        /// <summary>
        /// create constant strings for each type of characters
        /// </summary>
        private static readonly string alphaCaps = "QWERTYUIOPASDFGHJKLZXCVBNM";
        private static readonly string alphaLow = "qwertyuiopasdfghjklzxcvbnm";
        private static readonly string numerics = "1234567890";
        private Random random = new Random();
        private static readonly string special = "@#$";

        #endregion Fields

        #region Methods (3)

        // Public Methods (1)

        /// <summary>
        /// Generates the strong password.
        /// </summary>
        /// <remarks>
        /// Generate four repeating random numbers are postions of lower, upper, numeric and special characters
        /// By filling these positions with corresponding characters,we can ensure the password has atleast one character of those types
        /// </remarks>
        /// <param name="length">The length.</param>
        /// <returns>password  string</returns>
        public string GenerateStrongPassword(int length)
        {
            StringBuilder generatedPassword = new StringBuilder(length);

            if (length < 4)
                throw new Exception("Number of characters should be greater than 4.");

            int pLower, pUpper, pNumber, pSpecial;
            string posArray = "0123456789";
            if (length < posArray.Length)
                posArray = posArray.Substring(0, length);
            pLower = GetRandomPosition(ref posArray);
            pUpper = GetRandomPosition(ref posArray);
            pNumber = GetRandomPosition(ref posArray);
            pSpecial = GetRandomPosition(ref posArray);

            for (int i = 0; i < length; i++)
            {
                if (i == pLower)
                    generatedPassword.Append(GetRandomChar(alphaCaps));
                else if (i == pUpper)
                    generatedPassword.Append(GetRandomChar(alphaLow));
                else if (i == pNumber)
                     generatedPassword.Append(GetRandomChar(numerics));
                else if (i == pSpecial)
                     generatedPassword.Append(GetRandomChar(special));
                else
                    generatedPassword.Append(GetRandomChar(allChars));
            }
            return generatedPassword.ToString();
        }
        // Private Methods (2)

        /// <summary>
        /// Gets the random char.
        /// </summary>
        /// <param name="fullString">The full string.</param>
        /// <returns></returns>
        private string GetRandomChar(string fullString)
        {
            return fullString.ToCharArray()[(int)Math.Floor(random.NextDouble() * fullString.Length)].ToString();
        }

        /// <summary>
        /// Gets the random position.
        /// </summary>
        /// <param name="posArray">The pos array.</param>
        /// <returns></returns>
        private int GetRandomPosition(ref string posArray)
        {
            string randomChar = posArray.ToCharArray()[(int) Math.Floor(random.NextDouble()
                                                                        *posArray.Length)].ToString();
            int pos = int.Parse(randomChar);
            posArray = posArray.Replace(randomChar, "");
            return pos;
        }

例如我们用上面的CODE生成一个长度为8位密码是：　ASSu#zO3，你可以写一个UI去显示它们了。

希望对您有帮助。

Author: Petter Liu   http://wintersun.cnblogs.com