A Regex replace case in .NET

Question

I am trying to replace all numbers in a <number></number> element as xxx if the number length is 15 or 16.

for example <number>1234567812345678</number> -> <number>xxx</number>

I did something like below but it replace the numbers even if their' length is bigger than 16. How to prevent this case ?

string test = "<number>1234567812345678</number><number>12345671234567</number><number>1234567123456712345678</number>";

test = Regex.Replace(test, @"([\d]{15,16})", "xxx");

Unwanted output

<number>xxx</number><number>12345671234567</number><number>xxx345678</number>

Wanted output

 <number>xxx</number><number>12345671234567</number><number>1234567123456712345678</number>

You want to specify that it is preceded by something that is not a digit and followed by something that is not a digit. — iCollect.it Ltd
– iCollect.it Ltd, Commented May 16, 2012 at 14:27

Kendall Frey · Accepted Answer · 2012-05-16 14:26:14Z

5

string test = "<number>1234567812345678</number><number>12345671234567</number><number>1234567123456712345678</number>";

test = Regex.Replace(test, @"(?<=>)\d{15,16}(?=<)", "xxx");

This makes sure that the number is preceded by a > and followed by a <, using lookaround.

answered May 16, 2012 at 14:26

Kendall Frey

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1 Comment

Barış Velioğlu Over a year ago

This is more exactly what I wanted. Thank you very much. I will mark it when I can.

Meta-Knight · Accepted Answer · 2012-05-16 16:49:06Z

2

You didn't specify that the numbers should be preceded by <number> and followed by </number>. You can do it like this:

test = Regex.Replace(test, @"(?<=<number>)([\d]{15,16})(?=</number>)", "xxx");

edited May 16, 2012 at 16:49

answered May 16, 2012 at 14:29

Meta-Knight

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Comments

Brian Geihsler · Accepted Answer · 2012-05-16 14:28:38Z

1

Regex by default will replace substrings unless you tell it how the string is supposed to end. You need to surround your [\d]{15,16} with matchers against the tag like this:

Regex.Replace(test, @"<number>[\d]{15,16}</number>", @"<number>xxx</number>");

answered May 16, 2012 at 14:28

Brian Geihsler

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