将十六进制值转换为utf-8字符

Question

I'm using IMAP class to read emails. When my mail body contains Ö IMAP returns the hex value: =C3=96 . How do I convert it to an utf-8 Ö?

I'm thinking something like :

Encoding enc = Encoding.GetEncoding("UTF-8);
System.Byte[] ch = new System.Byte[1];

ch[0] = System.Convert.ToByte([hex value of Ö], 16);
var decodedItem = enc.GetString(ch);

Where expected value of decodedItem is Ö. But I don't really know why Ö translates to =C3=96 in IMAP and I can't send that in to ToByte() because =C3=96 isnt a true hex value.

I've also tried doing this:

Encoding enc = Encoding.GetEncoding("UTF-8);
System.Byte[] ch = new System.Byte[1];

ch[0] = 214;
var decodedItem = enc.GetString(ch);

But the value in decodedItem is =

Answer 1

That symbol is actually two bytes (0xC3, 0x96), but you're only assigning one, and a different one at that (214 = 0xD6)...

Encoding enc = Encoding.GetEncoding("UTF-8");
System.Byte[] ch = { 0xC3, 0x96 };

var decodedItem = enc.GetString(ch);

To clarify a bit further, 0xD6 (214) is actually for Unicode, not UTF-8, and you'd reach it by changing the call and values to match the Unicode value:

Encoding enc = Encoding.GetEncoding("Unicode");
System.Byte[] ch = { 0xD6, 0x00 };

Answer 2

http://www.utf8-chartable.de/ U+00D6 Ö c3 96 LATIN CAPITAL LETTER O WITH DIAERESIS

This means you have to take away the '=' and then convert it to UTF 8

I hope this helps.

Greetings Alex

Answer 3

There's no Unicode in most of today's e-mails. In order to arrive to a Unicode text, you have to do the following operations:

• Find a textual part of the message. There could be many of them. See the BODYSTRUCTURE in RFC 3501.
• Inspect the MIME headers (or the BODYSTRUCTURE response) to find out the Content-Transfer-Encoding of the part that you're looking at. Most common encodings are quoted-printable and base64 . Look at RFC 2045, 2046, 2047 and 2048 for details.
• Undo the Content-Transfer-Encoding so that you arrive at a bytestream which contains a sequence of bytes.
• Look at the Content-Type header, the charset parameter.
• Decode the stream of bytes using a codec/charset/... which you find above.
• Congratulations, you now have your Unicode string.

Alternatively, use a library which implements these functions in your favorite language/framework. There are plenty of them.