VB.NET Use Regex to split string on single commas, but not on double commas

Question

There's a file I'm trying to use for a list of strings that has the following rules:

Cannot begin or end with an unescaped comma.
A comma is escaped by a preceding comma.
Strings are separated by unescaped commas.
Everything else is absolutely face-value.

I've been fiddling around with some VB.NET code to parse a file like this and split it up into either a String() or a List(Of String), but it's gotten to be a little annoying. It's not that I can't figure this out; it's that I don't want to write crap code. If it's unnecessarily confusing, unecessarily slow, or anything else like that, it's not good enough.

Now, I know this almost starts to sound a little like a Code Review question, but I'm really starting to think that maybe a good regex would work better than trying to do this programmatically. Unfortunately regexes are not easy to work with, and while using one to tell it to escape on a comma may be a trivial matter, getting it to also ignore double commas and such is a bit more of an issue, at least for somebody who's not used to regexes.

How do you do this (properly) in VB.NET? In particular, I'm having a little bit of trouble putting together a wild card that'll match anything at all but a comma. It's also taking me a little bit to find out whether #1 has to be verified programmatically, or whether it can be done in the regex itself at the same time as the split operation.

EDIT

I just "woke up" and realized that this syntax is ambiguous, since in an odd-numbered series of three or more commas, you don't know what's escaped and what isn't. I'm just going to accept the current answer and move on.

@AvinashRaj I've got a regex reference in front of me; I'm still looking through it and trying to put something together to try. In particular, It's taking me a little while to find something that says "any character at all but this particular one". — Panzercrisis
– Panzercrisis, Commented Oct 13, 2014 at 19:14

Drejc · Accepted Answer · 2014-10-13 19:13:00Z

2

Haven't used VB.net in a long time ... but I would't got the RegEx way.

What about splitting the string by "," ...

Dim parts As String() = s.Split(New Char() {","c})

You will get a list of items, now you only need to take care of the empty items (escaped commas) and join them with the correct preceding item.

PS: not sure if split gives you empty items in case of ",,"

answered Oct 13, 2014 at 19:13

Drejc

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2 Comments

Panzercrisis Over a year ago

Is using this and the concatenation a lot more efficient than regex?

Drejc Over a year ago

The code will be simpler to understand than a RegEx, not even sure if this can be done via RegEx. And probably faster, but without testing hard to tell.

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