md5

 string str = "123456";
            MD5 md5 = new MD5CryptoServiceProvider();
            byte[] fromData = System.Text.Encoding.UTF8.GetBytes(str);
            byte[] targetData = md5.ComputeHash(fromData);
            string byte2String = null;
            for (int i = 0; i < targetData.Length; i++)
            {
                byte2String += targetData[i].ToString("x"); // 字母小写  反之大写 
            }