一：字符串加密：    public static String GetMD5(string input)            {               System.Security.Cryptography.MD5CryptoServiceProvider  x=newSystem.Security.Cryptography.MD5CryptoServiceProvider();                byte[]bs =System.Text.Encoding.UTF8.GetBytes(input);                bs =x.ComputeHash(bs);                System.Text.StringBuilder s =newSystem.Text.StringBuilder();                foreach(byte b inbs)                {                    s.Append(b.ToString("x2").ToLower());                }                returns.ToString();            }    public static string GetMD5(string sDataIn)          {              MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();              byte[] bytValue, bytHash;              bytValue = System.Text.Encoding.UTF8.GetBytes(sDataIn);              bytHash = md5.ComputeHash(bytValue);              md5.Clear();              string sTemp = "";              for (int i = 0; i < bytHash.Length; i++)              {                  sTemp += bytHash[i].ToString("X").PadLeft(2, '0');              }              return sTemp.ToLower();          }    二：文件加密：    /// <summary>          /// 计算文件MD5值          /// </summary>          /// <param name="str">需要计算的文件路径</param>          /// <returns>MD5值</returns>          public static string MD5Value(String filepath)          {              MD5 md5 = new MD5CryptoServiceProvider();              byte[] md5ch;              using (FileStream fs = File.OpenRead(filepath))              {                  md5ch = md5.ComputeHash(fs);              }                         md5.Clear();              string strMd5 = "";              for (int i = 0; i < md5ch.Length - 1; i++)              {                  strMd5 += md5ch[i].ToString("x").PadLeft(2, '0');              }              return strMd5;          }