Format string with regex and replace value

Question

I have a collection of rows where the DateTime is not correct.

Is it possible to correct them with Regex.Replace?

    Wed2,8-Jul-21 64 53,0 57 
    Thu2, 9-Jul-21 73 60,0 48
    Fri, 30-Jul-21 86 70,0 36
    Sat,31-Jul-21 84 69,0 38
    Sun0, 1-Aug-21 89 73,0 33
    Mon0,2-Aug-21 98 80,0 24 
    Tue0, 3-Aug-21 91 75,0 31
    Wed0,4-Aug-21 92 75,0 30

    foreach (var row in rows)
    {
        Regex rg = new Regex([pattern]);
        rg.Replace(row, [replacement]);
    }

The wrong data is in the dateTime value; see below:

This is not correct: Wed2,8-Jul-21

The correct value is: Wed,28-Jul-21

Also, This is not correct: Thu2, 9-Jul-21

The correct value is: Thu,29-Jul-21

Surely it's possible. But which lines are not correct and what are the desired outcomes? — Marco
– Marco, Commented Aug 5, 2021 at 13:18
You could match index 3 and 5 of the string and check if they're numbers or white-space, and replace them with an empty string, either with regex or string manipulation. I recommend learning regex and reading stackoverflow.com/help/how-to-ask, as the question you've proposed is lacking in research — pyknight202
– pyknight202, Commented Aug 5, 2021 at 13:58

Chris Maurer · Accepted Answer · 2021-08-05 14:20:53Z

2

If the only problem is transposed characters, then do this for your pattern:

(Mon|Tue|Wed|Thu|Fri|Sat|Sun)(\d), *(\d)

Replace with

$1, $2$3

edited Aug 5, 2021 at 14:20

answered Aug 5, 2021 at 14:11

Chris Maurer

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3 Comments

Saeid Mirzaei Over a year ago

@Chriss Maurer Thanks, but the main issue is on the first example. pls look at my comment on Good Night Nerd Pride. It is not working.

Arsey Over a year ago

@Chris Maurer I don't know if it's mandatory to not have space or not, but with your current example there is a space between Fri, and 30 -> "Fri, 30-Jul-21 86 70,0 36"

Chris Maurer Over a year ago

Yes, it cleans it up and makes each date a consistent format. It is customary to put a space after the comma, but if it is not desired it can be removed from the replacement and all results will consistently have no space between the comma and the day.

Good Night Nerd Pride · Accepted Answer · 2021-08-05 14:02:15Z

0

This is one way to do it:

var rows = new[]
{
    "Wed2,8-Jul-21 64 53,0 57",
    "Thu2, 9-Jul-21 73 60,0 48",
    "Fri, 30-Jul-21 86 70,0 36",
    "Sat,31-Jul-21 84 69,0 38",
    "Sun0, 1-Aug-21 89 73,0 33",
    "Mon0,2-Aug-21 98 80,0 24",
    "Tue0, 3-Aug-21 91 75,0 31",
    "Wed0,4-Aug-21 92 75,0 30"
};

var rg = new Regex(@"^(\w{3})\d?, ?(\d.*)");

foreach (var row in rows)
{
    var fixedRow = rg.Replace(row, "$1,$2");
    Console.WriteLine(fixedRow);
}

Working example: https://dotnetfiddle.net/uAMx06

Explanation:

The general idea is to match the parts you are interested in, store them with capture groups, and then rebuild a fixed string from those components.

^          Matches the beginning of the input.
(          Starts a capture group. Everything that is matched
             between '(' and ')' will be stored and can be
             referenced with $1.
\w{3}      Matches any word character exactly three times.
)          Closes the capture group.
\d?        Matches a digit 0 or 1 times.
,          Matches a literal ','.
 ?         Matches a space character 0 or 1 times.
(          Starts another capture group, referenced with $2.
\d         Matches a single digit.
.*         Matches any string of characters
)          Closes the last capture group.

edited Aug 5, 2021 at 14:02

answered Aug 5, 2021 at 13:52

Good Night Nerd Pride

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3 Comments

Saeid Mirzaei Over a year ago

Thanks for your answer. but in the first one shouldn't remove 2. the correct value is Wed,28-Jul-21 64 53,0 57

Saeid Mirzaei Over a year ago

Thanks for the cool explanation. I made a small change in your pattern. ^(\w{3})(\d)?, ?(\d.*) and replacement is $1,$2$3

Chris Maurer Over a year ago

Just an observation that this regex pattern overmatches the error condition and "corrects" cases like Fri, 30-Jul-21, making it work harder than it has to. I'd remove the first ?.

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