How to parse an alphanumeric string to get a numeric value

Question

If I have a strings like

[1] Bryan Mar

John Doe [2]

Mary [3] Cole

How would i get the value inside the [] if it is randomly located in each string.

I was thinking of regular expressions but I don't know how to create a pattern for this example.

Thanks for your help.

Update Numbers inside the [] is a 32bit integer

Even if the proposed duplicate is javascript it is a duplicate since the only thing you need is the regex. — Tim Schmelter, Jun 10 '14 at 11:27
http://stackoverflow.com/questions/1717611/regex-c-sharp-find-a-string-between-2-known-values — Ehsan Sajjad, Jun 10 '14 at 11:30
@TimSchmelter Especically as the proposed duplicate question actually contains the answer for c# in the question itself — Bob Vale, Jun 10 '14 at 11:32
@TimSchmelter Ok I read too fast and read that as c# because change that to `var regex = new Regex(@"(?<=\[)[0-9]+(?=\])")` and its correct for c# — Bob Vale, Jun 10 '14 at 11:54

Klaus Byskov Pedersen · Accepted Answer · 2014-06-10T11:36:42.903

1

You are right that using a regular expression would be a one way to solve it. Try this:

class Program
{
    static void Main(string[] args)
    {
        var strings = new string[] { "[1] Bryan Mar", "John Doe [2]", "Mary [3] Cole" };

        var re = new Regex(@"^.*\[(\d)\].*$");

        foreach (var s in strings)
        {
            var m = re.Match(s);
            if (m.Success)
            {
                Console.WriteLine(m.Groups[1].Value);
            }
        }

        Console.ReadLine();
    }
}

The expression matches zero or more characters followed by an opening square bracket, followed by a single digit (\d) and a closing square bracket and then any number of characters. The enclosing parenthesis adds the captured digit to a regular expression group which can be accessed later (in m.Groups[1]). If you wonder why the group has index 1 and not index 0, it is because the entire string is always group 0.

If you want it to be able to match more than one digit, simply change the expression to:

var re = new Regex(@"^.*\[(\d+)\].*$");

edited Jun 10 '14 at 11:36

answered Jun 10 '14 at 11:28

Klaus Byskov Pedersen

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That would only match once and also would only match single digits – Bob Vale Jun 10 '14 at 11:31
can you please explain the expression a little – Ehsan Sajjad Jun 10 '14 at 11:31
@BobVale that is correct, as per the examples. – Klaus Byskov Pedersen Jun 10 '14 at 11:33
@KlausByskovPedersen Doh, I read it as a single string including linefeeds. – Bob Vale Jun 10 '14 at 11:34
@EhsanSajjad, yes, I have done that now. – Klaus Byskov Pedersen Jun 10 '14 at 11:37
its having problem with more than one digit – Philip Badilla Jun 10 '14 at 11:37
Sir @KlausByskovPedersen could you make it work for more than one digit number? – Philip Badilla Jun 10 '14 at 11:38

How to parse an alphanumeric string to get a numeric value

1 Answers1