Base64编码/解码

        /// <summary>
        /// Base64编码
        /// </summary>
        /// <param name="str">字符串</param>
        /// <returns></returns>
        public string StringToBase64(string str)
        {
            var bytes = System.Text.Encoding.UTF8.GetBytes(str);
            return Convert.ToBase64String(bytes);
        }

        /// <summary>
        /// Base64解码
        /// </summary>
        /// <param name="str">字符串</param>
        /// <returns></returns>
        public string Base64ToString(string str)
        {
            var outputb = Convert.FromBase64String(str);
            return System.Text.Encoding.UTF8.GetString(outputb);
        }