Format string with regex in c#

Question

I would like to format a string that looks like this

BPT4SH9R0XJ6

Into something that looks like this

BPT4-SH9R-0XJ6

The string will always be a mix of 12 letters and numbers

Any advice will be highly appreciated, thanks

Not really, just figured that is whats most usually recommended — Eric Herlitz
– Eric Herlitz, Commented Apr 23, 2012 at 18:38
Will it always be same, i mean, add a dash(-) after every 4 characters? — sarwar026
– sarwar026, Commented Apr 23, 2012 at 18:39

Olly · Accepted Answer · 2012-04-23 18:41:09Z

33

Try Regex.Replace(input, @"(\w{4})(\w{4})(\w{4})", @"$1-$2-$3");

Regex is often derided, but is a pretty neat way of doing what you need. Can be extended to more complex requirements that are difficult to meet using string methods.

answered Apr 23, 2012 at 18:41

Olly

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3 Comments

Eric Herlitz Over a year ago

Thats exactly what I was looking for, I know this can be done with substr etc but string concatenation often gets complex and is not very fun to write either :)

Zanidd Over a year ago

is there a way to say $1.toLower() or similar?

Olly Over a year ago

@Zanidd Yes, there's an overload of Replace() that allows you to use a custom function to generate the replacement string.

Sergey Kalinichenko · Accepted Answer · 2012-04-23 18:38:56Z

6

You can use "(.{4})(.{4})(.{4})" as your expression and "$1-$2-$3" as your replacement. This is, however, hardly a good use for regexp: you can do it much easier with Substring.

var res = s.Substring(0,4)+"-"+s.Substring(4,4)+"-"+s.Substring(8);

answered Apr 23, 2012 at 18:38

Sergey Kalinichenko

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Comments

MiMo · Accepted Answer · 2012-04-23 19:48:38Z

4

If the rule is to always split in three block of four characters no need for a reg exp:

str.Substring(0,4) + "-" + str.Substring(4,4) + "-" + str.Substring(8,4)

edited Apr 23, 2012 at 19:48

answered Apr 23, 2012 at 18:40

MiMo

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Servy · Accepted Answer · 2012-04-23 18:39:12Z

3

It would seem that a combination of String.Concat and string.Substring should take care of everything that you need.

answered Apr 23, 2012 at 18:39

Servy

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Nesim Razon · Accepted Answer · 2012-04-23 18:42:01Z

2

  var str = "BPT4SH9R0XJ6";
  var newStr = str.Substring(0, 4) + "-" + str.Substring(4, 4) + "-" + str.Substring(8, 4);

answered Apr 23, 2012 at 18:42

Nesim Razon

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naspinski · Accepted Answer · 2012-04-23 18:53:09Z

2

Any reason you want to do a regex? you could just insert hyphens:

string s = "BPT4SH9R0XJ6";
for(int i = 4; i < s.length; i = i+5)
    s = s.Insert(i, "-");

This would keep adding hyphens every 4 characters, would not error out if string was too short/long/etc.

edited Apr 23, 2012 at 18:53

answered Apr 23, 2012 at 18:42

naspinski

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1 Comment

Tom Pažourek Over a year ago

Are you sure the code is correct? You are not using the i variable. Also it's not very efficient since it creates new string object in every iteration.

sarwar026 · Accepted Answer · 2012-04-23 18:42:59Z

1

return original_string.SubString(0,4)+"-"+original_string.SubString(4,4)+"-"+original_string.SubString(8,4);

answered Apr 23, 2012 at 18:42

sarwar026

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Steve Wong · Accepted Answer · 2012-04-23 18:45:05Z

1

string str = @"BPT4SH9R0XJ6";
string formattedString = string.Format("{0}-{1}-{2}", str.Substring(0, 4), str.Substring(4,4), str.Substring(8,4));

answered Apr 23, 2012 at 18:45

Steve Wong

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ChaseTheSun · Accepted Answer · 2013-02-28 12:49:11Z

1

This works with any length of string:

            for (int i = 0; i < (int)Math.Floor((myString.Length - 1) / 4d); i++)
            {
                myString = myString.Insert((i + 1) * 4 + i, "-");
            }

answered Feb 28, 2013 at 12:49

ChaseTheSun

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Eric Herlitz · Accepted Answer · 2012-04-23 18:44:27Z

0

Ended upp using this

var original = "BPT4SH9R0XJ6".ToCharArray();

var first = new string(original, 0, 4);
var second = new string(original, 4, 4);
var third = new string(original, 8, 4);
var mystring = string.Concat(first, "-", second, "-", third);

Thanks

answered Apr 23, 2012 at 18:44

Eric Herlitz

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Primc · Accepted Answer · 2012-04-23 18:58:05Z

0

If you are guaranteed the text you're operating on is the 12 character code then why don't you just use substring? Why do you need the Regex?

String theString = "AB12CD34EF56";
String theNewString = theString.Substring(0, 4) + "-" + theString.Substring(4, 4) + "-" + theString.Substring(8, 4);'

answered Apr 23, 2012 at 18:58

Primc

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