//计算字符串的MD5值
        public 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();
        }
       

        //计算文件的MD5值
        public 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;
        }