#region 将Base64编码的文本转换成普通文本        /// <summary>        /// 将Base64编码的文本转换成普通文本        /// </summary>        /// <param name="base64">Base64编码的文本</param>        /// <returns></returns>        public static string Base64StringToString(string base64)        {            if (base64 != "")            {                char[] charBuffer = base64.ToCharArray();                byte[] bytes = Convert.FromBase64CharArray(charBuffer, 0, charBuffer.Length);                string returnstr = Encoding.Default.GetString(bytes);                return returnstr;            }            else            {                return "";            }        }        #endregion        #region 字符串转为base64字符串        public static string changebase64(string str)        {            if (str != "" && str != null)            {                byte[] b = Encoding.Default.GetBytes(str);                string returnstr = Convert.ToBase64String(b);                return returnstr;            }            else            {                return "";            }        }        #endregion