C# regex handle newline in headers

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I am reading the headers of an email message where the headers look like this:

Date: 24 Apr 2023 09:43:44 +0200
Subject: HELP! Location 'Name249fc8e9-068b-47c3-a39c-a3e4cdfe2c16' is not
 responding!
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: quoted-printable

As you can see subject has a new line character, which needs to be a part of the subject header within my regex.

What I have tried:

The regex pattern

Quote:
.*?:\s.*

matches almost all of it, but the subject will miss the " responding!" part. How can I add the rest of the subject part and still get everything else.

I tried looking into lookarounds, but I dont know if this is the right way to do it. Any suggestions?

Posted 23-Apr-23 22:15pm

Evilfish2000

Updated 24-Apr-23 1:06am

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Richard Deeming 24-Apr-23 5:09am

Rather than reinventing the wheel, why not use the battle-tested library that Microsoft recommend: MimeKit[^].

Evilfish2000 24-Apr-23 6:45am

Could you post that comment as a solution cause this is just what I needed and more.

PIEBALDconsult 24-Apr-23 9:31am

The dot doesn't match linefeeds by default. A bit inconvenient that it does match carriage return. Use the Singleline option.

Specifies single-line mode. Changes the meaning of the dot (.) so it matches every character (instead of every character except \n).

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Richard Deeming · Accepted Answer · 2023-04-24T01:06:00

Solution 1

As discussed in the comments, Microsoft officially recommend using MimeKit[^] for all email-related code.

It's free and open-source, and it's actively maintained:
GitHub - jstedfast/MimeKit: A .NET MIME creation and parser library with support for S/MIME, PGP, DKIM, TNEF and Unix mbox spools.[^]

Posted 24-Apr-23 1:06am

Richard Deeming

Comments

PIEBALDconsult 24-Apr-23 10:13am

That may be what the OP needs, but it doesn't answer the question he asked.

Richard Deeming 24-Apr-23 10:17am

Which is why I originally posted it as a comment. The OP then asked me to post it as a solution, since it solves his real question, rather than the question he asked. :)

Evilfish2000 24-Apr-23 10:47am

It's true that the answer is not strictly correct with the answer. But, I was trying to read the headers of emails and the meme kit does exactly that.

C# regex handle newline in headers

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C# regex handle newline in headers

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