blocks|key|168280|text|身体数据似乎是be+64+not编码的，而不是be+64编码的。不同之处在于在编码的64个字符中使用了-和_，而不是%2B和/。一种解决方案是在调用FromBase64String之前分别用%2B和/替换所有字符和_字符。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|168281|请参阅https://www.rfc-editor.org/rfc/rfc4648#section-5|offset|length|168282|entityMap|0|LINK|mutability|MUTABLE|url|https://www.rfc-editor.org/rfc/rfc4648#section-5^0|0|3|1C|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

The body data appears to be base64url-encoded, not base64-encoded.
The difference is the use of - and _, instead of + and /, in the encoding’s alphabet of 64 characters.
One solution is to replace all - and _ characters with + and / respectively, before calling FromBase64String.
See <a href="https://www.rfc-editor.org/rfc/rfc4648#section-5" rel="nofollow noreferrer">https://www.rfc-editor.org/rfc/rfc4648#section-5</a>

blocks|key|168287|text|下面是我最后使用的代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|168288|++++++++++++++++foreach+(MessagePart+p+in+m.Payload.Parts)
++++++++++++++++{
++++++++++++++++++++if+(p.MimeType+==+"text/html")
++++++++++++++++++++{
+++++++++++++++++++++++++byte[]+data+=+FromBase64ForUrlString(p.Body.Data);
+++++++++++++++++++++++++string+decodedString+=+Encoding.UTF8.GetString(data);
+++++++++++++++++++++++++Response.Write(decodedString);++++++++++++++++++++++++++++
++++++++++++++++++++}
++++++++++++++++}|code-block|syntax|javascript|168289|……|168290|++++public+static+byte[]+FromBase64ForUrlString(string+base64ForUrlInput)
++++{
++++++++int+padChars+=+(base64ForUrlInput.Length+%25+4)+==+0+?+0+:+(4+-+(base64ForUrlInput.Length+%25+4));
++++++++StringBuilder+result+=+new+StringBuilder(base64ForUrlInput,+base64ForUrlInput.Length+%2B+padChars);
++++++++result.Append(String.Empty.PadRight(padChars,+'='));
++++++++result.Replace('-',+'%2B');
++++++++result.Replace('_',+'/');
++++++++return+Convert.FromBase64String(result.ToString());
++++}|168291|好文章http://www.codeproject.com/Tips/76650/Base-base-url-base-url-and-z-base-encoding|offset|length|168292|entityMap|0|LINK|mutability|MUTABLE|url|http://www.codeproject.com/Tips/76650/Base-base-url-base-url-and-z-base-encoding^0|0|0|0|0|3|28|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|Z|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|10|8|@]|9|@$M|11|N|12|1|13]]|A|$]]|$1|O|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

Here is the code I ended up using:

<pre><code> foreach (MessagePart p in m.Payload.Parts)
 {
 if (p.MimeType == "text/html")
 {
 byte[] data = FromBase64ForUrlString(p.Body.Data);
 string decodedString = Encoding.UTF8.GetString(data);
 Response.Write(decodedString); 
 }
 }
</code></pre>

....

<pre><code> public static byte[] FromBase64ForUrlString(string base64ForUrlInput)
 {
 int padChars = (base64ForUrlInput.Length % 4) == 0 ? 0 : (4 - (base64ForUrlInput.Length % 4));
 StringBuilder result = new StringBuilder(base64ForUrlInput, base64ForUrlInput.Length + padChars);
 result.Append(String.Empty.PadRight(padChars, '='));
 result.Replace('-', '+');
 result.Replace('_', '/');
 return Convert.FromBase64String(result.ToString());
 }
</code></pre>

Good article <a href="http://www.codeproject.com/Tips/76650/Base-base-url-base-url-and-z-base-encoding" rel="noreferrer">http://www.codeproject.com/Tips/76650/Base-base-url-base-url-and-z-base-encoding</a>

blocks|key|2274659|text|在这个页面上https://developers.google.com/gmail/api/v1/reference/users/messages/attachments/get|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2274660|您可以发现有一个.NET示例，其中包含用于解码的代码：|2274661|//+Converting+from+RFC+4648+base64-encoding
//+see+http://en.wikipedia.org/wiki/Base64#Implementations_and_history
String+attachData+=+attachPart.Data.Replace('-',+'%2B');
attachData+=+attachData.Replace('_',+'/');
byte[]+data+=+Convert.FromBase64String(attachData);|code-block|syntax|javascript|2274662|entityMap|0|LINK|mutability|MUTABLE|url|https://developers.google.com/gmail/api/v1/reference/users/messages/attachments/get^0|6|2B|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

On this page <a href="https://developers.google.com/gmail/api/v1/reference/users/messages/attachments/get" rel="nofollow">https://developers.google.com/gmail/api/v1/reference/users/messages/attachments/get</a>

you can find that there is a .NET example with this code for decoding:

<pre><code>// Converting from RFC 4648 base64-encoding
// see http://en.wikipedia.org/wiki/Base64#Implementations_and_history
String attachData = attachPart.Data.Replace('-', '+');
attachData = attachData.Replace('_', '/');
byte[] data = Convert.FromBase64String(attachData);
</code></pre>

blocks|key|2274674|text|现在，WebEncoders.Base64UrlDecode程序集中的Microsoft.AspNetCore.WebUtilities方法可以对此进行解码：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2274675|var+bytes+=+WebEncoders.Base64UrlDecode(data);|code-block|syntax|javascript|2274676|entityMap|0|LINK|mutability|MUTABLE|url|https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.webutilities.webencoders.base64urldecode|1|https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.webutilities^0|3|R|0|Z|X|1|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]|$A|W|B|X|1|Y]]|C|$]]|$1|D|3|E|5|F|7|Z|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|10|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]|Q|$5|L|M|N|C|$O|R]]]]

The <a href="https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.webutilities.webencoders.base64urldecode" rel="nofollow noreferrer">WebEncoders.Base64UrlDecode</a> method in the <a href="https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.webutilities" rel="nofollow noreferrer">Microsoft.AspNetCore.WebUtilities</a> assembly can decode this now:
<pre><code>var bytes = WebEncoders.Base64UrlDecode(data);
</code></pre>

I'm trying to pull out the subject and body of an email with .Net. It seems to go OK except for the text/html MessagePart. I'm not sure of the encoding etc - has anybody got this working OK? It errors for me when trying to convert.

Here is the raw string for the text/html Body Data

"PGRpdiBkaXI9Imx0ciI-dGV4dCBpbiBoZXJlPGJyPjwvZGl2Pg0K"

which throws an error.

"The input is not a valid Base-64 string as it contains a non-base 64 character, more than two padding characters, or an illegal character among the padding characters."

Here is the code:

<pre><code> UsersResource.MessagesResource.GetRequest gr = gs.Users.Messages.Get(userEmail, TextBox1.Text);
 gr.Format = UsersResource.MessagesResource.GetRequest.FormatEnum.Full; 
 Message m = gr.Execute();

 foreach (MessagePart p in m.Payload.Parts)
 {
 if (p.MimeType == "text/html")
 {
 try
 {
 byte[] data = Convert.FromBase64String(p.Body.Data);
 string decodedString = Encoding.UTF8.GetString(data);
 Response.Write(decodedString);
 }
 catch (Exception ex) { }
 }
 }
</code></pre>

I'm getting the decoding wrong???

Thanks for your help.

Having trouble reading the text/html message part

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我试图拿出一个主题和正文的电子邮件与.Net。除了text/html MessagePart之外，它似乎进行得很好。我不确定编码等--有人能正常工作吗？这是错误的时候，我试图转换。以下是文本/html正文数据的原始字符串"PGRpdiBkaXI9Imx0ciI-dGV4dCBpbiBoZXJlPGJyPjwvZGl2P...

问无法读取文本/html消息部分
EN

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