Re: Regex question

Hello tshad,

I have a text string that has a date in it and I am trying to pull out
the date. In my earlier posts I got a couple of patterns that seem
correct, but I can't seem to get them to work. I want to account for
1 or 2 digits in the month and day fields and 2 or 4 in the year
field.

After not getting the correct result I put it down to the simplest
pattern which would match exactly the number of digits and I get
nothing.

For example, if I have the following string:

valueIn = "At 02/23/2007 DOM";

I want to end up with 02/23/2007.

If I use:

Match oMatch;
oMatch = Regex.Match(valueIn, @"\d{2}/\d{2}/\d{4}");
I get nothing from my oMatch.Groups[1].Value.

If I have:

oMatch = Regex.Match(valueIn, @"\d{1,2}/\d{1,2}/\d{2,4}");
strValue = oMatch.Groups[1].Value;
I get nothing from my oMatch.Groups[1].Value;

If I have:

oMatch = Regex.Match(valueIn,
@"\d{1,2}(-|/)\d{1,2}(-|/)(\d{2}|\d{4})");
strValue = oMatch.Groups[1].Value;
oMatch.Groups[1].Value = "/"
oMatch.Groups[2].Value = "/"
oMatch.Groups[3].Value = "20"
What is happening here?

I would have expected the 1st one to work which I assume says look for
a pattern of: 2 digits, a slash, 2 more digits, another slass and 4
digits which is in this string.

Not sure why it found the slashes and the 20 in the last set up.

Tom, this is due to the fact that () create groups. So if your regex contains () it will automatically create grouped values in your match object.

In your case there is no need to use groups at all, so you can change your code to:

if (oMatch.Success)
{
string unparsedDate = oMatch.Value;
}

Alternatively, if you want to use groups, or want to learn more about groups:

use this regex
@"(\d{1,2})[-/](\d{1,2})[-/](\d{2}|\d{4})";

Now oMatch.Groups[1].Value will contain the month
Now oMatch.Groups[2].Value will contain the day
Now oMatch.Groups[3].Value will contain the year

Also note that I changed (-|/) to [-/], so that it doesn't give me more groups than I actually need...


--
Jesse Houwing
jesse.houwing at sogeti.nl


.

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