/// <summary>    /// 獲取文件MD5值    /// </summary>    /// <param name="fileName">文件絕對路徑</param>    /// <returns>MD5值</returns>    public static string GetMD5HashFromFile(string fileName)    {      try      {        FileStream file = new FileStream(fileName, FileMode.Open);        System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();        byte[] retVal = md5.ComputeHash(file);        file.Close();        StringBuilder sb = new StringBuilder();        for (int i = 0; i < retVal.Length; i++)        {          sb.Append(retVal[i].ToString("x2"));        }        return sb.ToString();      }      catch (Exception ex)      {        throw new Exception("GetMD5HashFromFile() fail,error:" + ex.Message);      }    }