CODEWITHSUNDEEP
c#regex
wootowl
wootowl

Reputation: 93

Confusion over Multiple Matches in a Regex

I've tested my regex in a regex tester and the statement itself appears that it should be working, however instead of matching 4 objects as it should, it only matches 1 (the entire string) which I'm not sure why its even doing that...

rgx = new Regex(@"^([0-9]+)\.([0-9]+)\.([0-9]+)\.([0-9]+)$");
matches = rgx.Matches("0.0.0.95");

at this point if I do:

foreach (Match m in matches)
{
    Console.WriteLine(m.Value);
}

it will just show "0.0.0.95" when it should be matching 0, 0, 0, and 95 and not the entire string. What am I doing wrong here?

ANSWER - The single match of the entire string contained the group matches I was looking for, accessed in this manner:

r.r1 = Convert.ToInt32(m.Groups[1].Value);
r.r2 = Convert.ToInt32(m.Groups[2].Value);
r.r3 = Convert.ToInt32(m.Groups[3].Value);
r.r4 = Convert.ToInt32(m.Groups[4].Value);

Upvotes: 1

Views: 51

Answers (1)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726709

In this case you don't get multiple matches - there is only one match in there, but it has four capturing groups:

    ^([0-9]+)\.([0-9]+)\.([0-9]+)\.([0-9]+)$
//   ^^^^^^^^  ^^^^^^^^  ^^^^^^^^  ^^^^^^^^
//   Group  1  Group  2  Group  3  Group  4
//   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
//                Group 0

There is a special group number zero that includes the entire match.

So you need to modify your program like this:

Console.WriteLine("One:'{0}' Two:'{1}' Three:'{2}' Four:'{3}'"
,   m.Groups[1].Value
,   m.Groups[2].Value
,   m.Groups[3].Value
,   m.Groups[4].Value
);

Upvotes: 3

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