Building regex expression in c#

Question

I have some string like this one:

DEV_NUM_26 - Some type...TYPE0 with support of some functions

My target is to get next data: (id=26, type=TYPE0)

Expression is looks like this:

    (?<id>(?<=DEV_NUM_) \d{0,3}) \s-\s (?<name>(?<=Some \s type \.+) \w+)

but I got 0 match results and the problem is in second (?<=). If I try to make something like:

    (?<id>(?<=DEV_NUM_) \d{0,3}) \s-\s (?<name>Some \s type \.+ \w+)

I got next result: (id=26, type=Some type...TYPE0).

The first and main question is how to fix this expression) And last but not least is why excluding prefix (?<=) doesn't work at the end of expression? As I understand, it suppose to find a part of expression in brackets and ignore it, like in the first part of expression, but it doesn't...

See hwnd's answer below for a working Regex. But for an explanation of why yours didn't work, it's because the second zero-width positive lookbehind ignored the fact that the preceding text was in fact present in the string being evaluated. So, (?<id>(?<=DEV_NUM_) \d{0,3}) \s-\s Some\stype\.+(?<name>(?<=Some \s type \.+) \w+) would work (but so verbose!), as would (?<id>(?<=DEV_NUM_) \d{0,3}) \s-\s [\w\d\s\.]+(?<name>(?<=Some \s type \.+) \w+) (less verbose, but still not as clean as hwnd's answer below). — Troy Gizzi
– Troy Gizzi, Commented Oct 23, 2014 at 21:56

hwnd · Accepted Answer · 2014-10-23 22:02:10Z

1

Instead, place the parts you don't want to include outside of your named capturing groups. Note: I removed the Positive Lookbehind assertions from your expression because they are really not necessary here.

String s = "DEV_NUM_26 - Some type...TYPE0 with support of some functions";
Match m  = Regex.Match(s, @"DEV_NUM_(?<id>\d{0,3})\s-\sSome\stype\.+(?<name>\w+)");
if (m.Success)
    Console.WriteLine(m.Groups["id"].Value);   //=> "26"
    Console.WriteLine(m.Groups["name"].Value); //=> "TYPE0"

If you want to shorten your expression, you could write it as ...

@"(?x)DEV_NUM_ (?<id>\d+) [^.]+\.+ (?<name>\w+)"

edited Oct 23, 2014 at 22:02

answered Oct 23, 2014 at 21:48

hwnd

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