public static class FileHelper    {        /// 
        /// 获取文件MD5值        /// 
        /// 文件绝对路径        /// 
     
      MD5值
             public static string GetFileMD5(string fileName)        {            try            {                using (System.IO.FileStream fs = new System.IO.FileStream(fileName, System.IO.FileMode.Open, System.IO.FileAccess.Read))                {                    return GetFileMD5(fs);                }            }            catch (Exception ex)            {                throw new Exception("GetMD5HashFromFile() fail,error:" + ex.Message);            }        }        /// 
        /// 获取文件MD5值        /// 
        /// 文件流        /// 
     
      MD5值
             public static string GetFileMD5(FileStream fs)        {            try            {                System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();                byte[] retVal = md5.ComputeHash(fs);                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("生成文件MD5是发生异常:" + ex.Message);            }        }    }