RegEx to match a specific format: 4 digits and 6 characters in a string

Question

I'm trying to design a RegEx in C# to match 4 digits and 6 characters in a string.

 string str = "Hello World! ABCD112233 fsdf sdfsdf 234324 fdsfds 4234 efwedf34ref dfsdf34f34f";

that matches only ABCD112233 in the above string.

Regex regex = new Regex("^[A-Za-z]{4}[0-9]{6}$", RegexOptions.Multiline);

How do I solve this problem?

All the words which has first 4 alphabets followed by 6 numbers. — Abhilash V, Apr 13 '19 at 15:00

g-dg · Accepted Answer · 2019-04-13T15:09:18.800

2

You would use the {n} quantifier to match a certain number of characters like so: [A-Za-z]{4}[0-9]{6}. This will match 4 letters (A-Z, a-z) and then 6 digits (0-9).

Note: don't use ^ and $ at the start and end as then it will only match if the whole word matches the regex.

edited Apr 13 '19 at 15:09

answered Apr 13 '19 at 15:00

g-dg

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You're right, but this one did not work - `Regex regex = new Regex("^[A-Za-z]{4}[0-9]{6}$", RegexOptions.Multiline)` – Abhilash V Apr 13 '19 at 15:03
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Is it because you are using `^` and `$` (which match the start and end of a given string)? – ProgrammingLlama Apr 13 '19 at 15:06
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@John is right. The `^` and `$` match the beginning and end of the string, respectively. This would only work if the whole string was like `ABCD112233`. – g-dg Apr 13 '19 at 15:08
Omg yes, you're so right. Thank you both :) – Abhilash V Apr 13 '19 at 15:09
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@AbhilashV You probably want [`\b`](https://www.regular-expressions.info/wordboundaries.html) at the start and end rather than `^` and `$`. – ProgrammingLlama Apr 13 '19 at 15:09

RegEx to match a specific format: 4 digits and 6 characters in a string

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