/// 
        /// 获取文件的md5摘要        /// 
        /// 文件流        /// 
     
      MD5摘要结果
             public static string GetAbstractToMD5(Stream sFile)        {            MD5 md5 = new MD5CryptoServiceProvider();            byte[] result = md5.ComputeHash(sFile);            StringBuilder sb = new StringBuilder(32);            for (int i = 0; i < result.Length; i++)            {                sb.Append(result[i].ToString("x").PadLeft(2, '0'));            }            return sb.ToString();        }        /// 
        /// 获取文件的md5摘要        /// 
        /// 文件流        /// 
     
      MD5摘要结果
             public static string GetAbstractToMD5(byte[] dataFile)        {            MD5 md5 = new MD5CryptoServiceProvider();            byte[] result = md5.ComputeHash(dataFile);            StringBuilder sb = new StringBuilder(32);            for (int i = 0; i < result.Length; i++)            {                sb.Append(result[i].ToString("x").PadLeft(2, '0'));            }            return sb.ToString();        }        /// 
        /// 签名字符串        /// 
        /// 需要签名的字符串        /// 密钥        /// 编码格式        /// 
     
      签名结果
             public static string Md5Sign(string prestr, string key, string _input_charset)        {            StringBuilder sb = new StringBuilder(32);            prestr = prestr + key;            MD5 md5 = new MD5CryptoServiceProvider();            byte[] t = md5.ComputeHash(Encoding.GetEncoding(_input_charset).GetBytes(prestr));            for (int i = 0; i < t.Length; i++)            {                sb.Append(t[i].ToString("x").PadLeft(2, '0'));            }            return sb.ToString();        }        /// 
        /// 验证签名        /// 
        /// 需要签名的字符串        /// 签名结果        /// 密钥        /// 编码格式        /// 
     
      验证结果
             public static bool Md5Verify(string prestr, string sign, string key, string _input_charset)        {            string mysign = Md5Sign(prestr, key, _input_charset);            if (mysign == sign)            {                return true;            }            else            {                return false;            }        }