.net base64编码解码

        public string decodestr(string str, Encoding Ens)
        {
            string ss = Ens.GetString(Convert.FromBase64String(str));
            return ss;
        }

        public string encodestr(string str, Encoding Ens)
        {
            string ss = Convert.ToBase64String(Ens.GetBytes(str));
            return ss;
        }