Base64編碼的字符串到字節數組C＃失敗

Question

我們正在從外部應用程序以表單主體接收base64編碼的字符串，下面是用於將字符串解碼為字節數組的代碼，但是我們遇到了異常

輸入字符串

PHBheW1lbnRSZXNwb25zZT48cmVzcG9uc2VDb2RlPjAwMDA8L3Jlc3BvbnNlQ29kZT48cmVzcG9uc2VDb2RlVGV4dD4wLVN1Y2Nlc3NmdWw8L3Jlc3BvbnNlQ29kZVRleHQ + PHJlc3BvbnNlU3VtbWFyeT5HUkVFTjwvcmVzcG9uc2VTdW1tYXJ5PjxwYXltZW50RXZlbnRJZGVudGlmaWVyPlRYTiAzNjM5PC9wYXltZW50RXZlbnRJZGVudGlmaWVyPjxMaXN0Pjxjb21wb25lbnRJRD5UWE4gMzYzOTwvY29tcG9uZW50SUQ + PGNsaWVudElEPkdPVERJU0UwNjwvY2xpZW50SUQ + PGJhbmtBdXRoQ29kZT5UOjEyMzQ8L2JhbmtBdXRoQ29kZT48YnV5bmV0VHhuSUQ + Mzc1PC9idXluZXRUeG5JRD48L0xpc3Q + PHBheW1lbnRJbnN0cnVtZW50UmVmPjwvcGF5bWVudEluc3RydW1lbnRSZWY + PG1hc2tlZENhcmROdW1iZXI + KioqKioqKioqKioqOTY4NjwvbWFza2VkQ2FyZE51bWJlcj48Y2FyZFR5cGU + TUFTVEVSQ0FSRDwvY2FyZFR5cGU + PGV4cGlyeURhdGU + MDMvMjAxNzwvZXhwaXJ5RGF0ZT48Y3VzdG9tRGF0YT4mbHQ7IVtDREFUQVsmbHQ7P3htbCB2ZXJzaW9uPSIxLjAiIGVuY29kaW5nPSJVVEYtOCI_Jmd0Ow0KJmx0O1RoaXN0bGVDdXN0b21EYXRhIHhtbG5zOnhzZD0iaHR0cDovL3d3dy53My5vcmcvMjAwMS9YTUxTY2hlbWEiIHhtbG5zOnhzaT0iaHR0cDovL3d3dy53My5vcmcvMjAwMS9YTUxTY2hlbWEtaW5zdGFuY2UiJmd0Ow0KICAmbHQ7T3JkZXJJZCZndDtCVFBQMzYzOSZsdDsvT3JkZXJJZCZndDsNCiAgJmx0O0Ftb3Vu dCZndDsxMjAmbHQ7L0Ftb3VudCZndDsNCiZsdDsvVGhpc3RsZUN1c3RvbURhdGEmZ3Q7XV0mZ3Q7PC9jdXN0b21EYXRhPjwvcGF5bWVudFJlc3B

例外

輸入內容不是有效的Base-64字符串，因為它包含非Base 64字符，兩個以上的填充字符或填充字符中的非法字符。

碼

var inputText = // use the data as shown above
byte[] decodedBytes = Convert.FromBase64String(inputText);

我想知道這是什么問題，為什么會引發異常，如果我嘗試在線轉換器，他們將在哪里返回正確的結果。

Answer 1

這是因為您的自定義數據無效。 在該Base64編碼的字符串中，您有一個原始的[CDATA]，很可能未正確編碼。

請注意，如果我采用您字符串的前684個字符，它將正確轉換為：

<paymentResponse><responseCode>0000</responseCode><responseCodeText>0-Successful</responseCodeText><responseSummary>GREEN</responseSummary><paymentEventIdentifier>TXN 3639</paymentEventIdentifier><List><componentID>TXN 3639</componentID><clientID>GOTDISE06</clientID><bankAuthCode>T:1234</bankAuthCode><buynetTxnID>375</buynetTxnID></List><paymentInstrumentRef></paymentInstrumentRef><maskedCardNumber>************9686</maskedCardNumber><cardType>MASTERCARD</cardType><expiryDate>03/2017</expiryDate><customData>&

但是當我們到達customData標記時，一切都變得混亂了 ，我想這包含了CDATA xml內容，該內容可能不是base64編碼的。

因此，可以將CDATA內容刪除，或者在將其添加到最終字符串之前對其進行正確編碼，以解決此問題。

Answer 2

謝謝大家的答復。

在研究了base64編碼的工作原理之后，我開始了這項工作。

下面是我用來修復它的代碼。

var input = new StreamReader(Request.InputStream).ReadToEnd();
        var inputText = "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_Jmd0Ow0KJmx0O1RoaXN0bGVDdXN0b21EYXRhIHhtbG5zOnhzZD0iaHR0cDovL3d3dy53My5vcmcvMjAwMS9YTUxTY2hlbWEiIHhtbG5zOnhzaT0iaHR0cDovL3d3dy53My5vcmcvMjAwMS9YTUxTY2hlbWEtaW5zdGFuY2UiJmd0Ow0KICAmbHQ7T3JkZXJJZCZndDtCVFBQMzYzOSZsdDsvT3JkZXJJZCZndDsNCiAgJmx0O0Ftb3VudCZndDsxMjAmbHQ7L0Ftb3VudCZndDsNCiZsdDsvVGhpc3RsZUN1c3RvbURhdGEmZ3Q7XV0mZ3Q7PC9jdXN0b21EYXRhPjwvcGF5bWVudFJlc3BvbnNlPg";
        inputText = ValidateBase64EncodedString(inputText);

        byte[] decodedBytes = Convert.FromBase64String(inputText);

        string xml = Encoding.UTF8.GetString(decodedBytes);

       private static string ValidateBase64EncodedString(string inputText)
        {
            string stringToValidate = inputText;
            stringToValidate = stringToValidate.Replace('-', '+'); // 62nd char of encoding
            stringToValidate = stringToValidate.Replace('_', '/'); // 63rd char of encoding
            switch (stringToValidate.Length % 4) // Pad with trailing '='s
            {
                case 0: break; // No pad chars in this case
                case 2: stringToValidate += "=="; break; // Two pad chars
                case 3: stringToValidate += "="; break; // One pad char
                default:
                    throw new System.Exception(
             "Illegal base64url string!");
            }

            return stringToValidate;
        }