Decoding Base64 / Quoted Printable encoded UTF8 string

Question

In my ASP.Net application working process, I need to do some work with string, which equals something like

=?utf-8?B?SWhyZSBCZXN0ZWxsdW5nIC0gVmVyc2FuZGJlc3TDpHRpZ3VuZyAtIDExMDU4OTEyNDY=?=

How can I decode it to normal human language?

Thanks in advance!

Update:

Convert.FromBase64String() does not work for string, which equals =?UTF-8?Q?Bestellbest=C3=A4tigung?=

I get The format of s is invalid. s contains a non-base-64 character, more than two padding characters, or a non-white space-character among the padding characters. exception.

Update:

Solution Here

Alternative solution

Update:

What kind of string encoding is that: Nweiß ???

Answer 1

This seems to be MIME Header Encoding. The Q in your second example indicates that it is Quoted Printable.

This question seems to cover the variants fairly well. In a quick search I didn't find any .NET libraries to decode this automatically, but it shouldn't be hard to do manually if you need to.

Answer 2

It's actually a base-64 string:

        string zz = "SWhyZSBCZXN0ZWxsdW5nIC0gVmVyc2FuZGJlc3TDpHRpZ3VuZyAtIDExMDU4OTEyNDY=";

        byte[] dd = Convert.FromBase64String(zz);

        // Returns Ihre Bestellung - Versandbestätigung - 1105891246
        string yy = System.Text.Encoding.UTF8.GetString(dd);

Answer 3

I've written a library that will decode these sorts of strings. You can find it at http://github.com/jstedfast/MimeKit

Specifically, take a look at MimeKit.Utils.Rfc2047.DecodeText()

Answer 4

That's not UTF8. Thats a Base64 encoded string.

the UTF-8 only indicates that the target string is in UTF8 format. After decoding the Base64 string:

SWhyZSBCZXN0ZWxsdW5nIC0gVmVyc2FuZGJlc3TDpHRpZ3VuZyAtIDExMDU4OTEyNDY=

You'll get the following result:

Ihre Bestellung - Versandbestätigung - 1105891246

See Base64 online decode/encode

Answer 5

Looks like a base64 string.

Try Convert.FromBase64String

http://msdn.microsoft.com/en-us/library/system.convert.frombase64string.aspx

Answer 6

This is an encoded word, which is used in email headers when there is non-ASCII content. Encoded words are defined in RFC 2047:

http://tools.ietf.org/html/rfc2047#section-2

The BNF for an encoded word is:

encoded-word = "=?" charset "?" encoding "?" encoded-text "?="

So the correct way to interpret this is:

1. The data is the stuff between the 3rd and 4th question marks
2. It has been Base64 encoded (the 'B' stands for Base64; if it were a 'Q' then it would be quoted-printable).
3. Once you decode the data, it will be in the UTF-8 character set.

The result, as @Shai correctly pointed out, is:

Ihre Bestellung - Versandbestätigung - 1105891246

This is German. The umlaut is obviously the reason for the UTF-8 and thus the need for an encoded word. The translation is:

Your order - Delivery confirmation - 1105891246

Apparently it's a tracking number for an order.

All modern email clients (and Outlook) transparently support encoded words.

Answer 7

This is a bit of guesswork, but let's try

• remove =? from start and ?= from end
• keep the start up to the next ? as the character set
• Remove the B? - don't know, what it is
• Convert the rest to a byte[] via System.Convert.FromBase64String()
• Convert this to the final String via Encoding.GetSTring() using the character set remembered in the second step