base64 与字符串互转

 #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