Match CSV line with semicolons and quotation inside a quoted string

Im trying to parse a single of a csv file. Curently it is done with some online regex webpage but in the end it has to be implemented in c#. (as reaction of some question in the comments)

I read a lot of other articels here on SO to figure it out by myself, but im stuck in solving it.

My test line for my RegExp looks like this (UPDATE: quotes escaped inside of quoted-strings):

~~;;"test123;weiterer Text";;"Test mit " Zeichen im Spaltenwert";nächste Spalte mit " Begrenzungszeichen;"4711";irgendwas 123,4;1222;"foo"test"~~

;;"test123;weiterer Text";;"Test mit "" Zeichen im Spaltenwert";nächste Spalte mit "" Begrenzungszeichen;"4711";irgendwas 123,4;1222;"foo""test"

; is the delimiter
" is the sign for quoted columns

Problem:

the line may contain empty columns (semicolon followed by semicolon without any text)
quoted strings may contain the quote sign, like here "Test mit " Zeichen im Spaltenwert"
the column delimiter may occure also in quoted strings, like here: "test123;weiterer Text"

What i have done so far with several googling and my limited understanding of regular expressions is this expression

(?<=^|;)(\".\"|[^;]*)|[^;]+

This gives following result

        [0] => 
        [1] => 
        [2] => "test123
        [3] => weiterer Text"
        [4] => 
        [5] => "Test mit " Zeichen im Spaltenwert"
        [6] => nächste Spalte mit " Begrenzungszeichen
        [7] => "4711"
        [8] => irgendwas 123,4
        [9] => 1222
        [10] => "foo"test"

Tested with https://www.myregextester.com/

The problem i have now is at the elements 2 and 3. This text

"test123;weiterer Text"

has to be one column but gets splited at the semicolon inside of the quoted string, although i thought i told the expression to match everysthing inside of quotation marks.

Any help here is highly appreciated. Thanks in advance.

Solution

Assuming a proper csv that uses doubled quotes for escaping (""), that is read line by line you can use

"(?:[^"]+|"")*"|[^;]+|(?<=;|^)(?=;|$)

Basically three different ways to match a column:

"(?:[^"]+|"")*" starting and closing quote with non-quotes or double quotes between
[^;]+ a series of non-semikolons
(?<=;|^)(?=;|$) an empty field between semikolons or between semikolon and start/end

Note:

if you want to use this in multiline context you would have to add \n in the negated character classes
it doesn't handle leading or trailing spaces connected with quoted fields

See https://regex101.com/r/twKZVN/1

(While regex 101 tests a PCRE pattern, all features used are also available in a .net pattern.