I need to validate the following string
case 1: 123E
The first three are numeric and then the alphabet.
I have created the following pattern
var pattern = @"^[0-9]{2}[a-zA-Z]{1}"
Is this correct?
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No. `[0-9]{2}` compares for 2 digits, not 3. – Maciej Los Jan 22 '21 at 08:35
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Almost there. `^\d{3}[a-zA-Z]$` should do. Where `\d` is shorthand for `[0-9]`. – JvdV Jan 22 '21 at 08:35
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var pattern = "^\d{3}[a-zA-Z]$", i am getting compilation error – tyu Jan 22 '21 at 08:48
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@tyu, I replied in an answer with a working `.Net` example. – JvdV Jan 22 '21 at 09:12
2 Answers
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Something like that should work: ^[0-9]{3}[a-zA-Z]$
You put {2} for numbers but in your case there are 3 of them so I wrote {3} instead.
You don't need to write {1} because [a-zA-Z] is enough to find exacly one letter.
I also added endline tag $ to ensure that there are no more symbols after letter.
Sergio
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You were close, as per my comment you can use:
^\d{3}[a-zA-Z]$
See the online demo
^- Start string anchor.\d{3}- Three digits where\dis shorthand for[0-9]1[a-zA-Z]- A single alpha char.$- End string anchor.
See a working .Net example here
1: This would only be the case if the ECMAScript flag is enabled. Otherwise \d is matching non-ascii digits as per this link. Thanks @WiktorStribiżew for noticing.
JvdV
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In .NET regex, when one wants to match ASCII digits, it [is safer](https://stackoverflow.com/questions/16621738/d-is-less-efficient-than-0-9) to use `[0-9]`. Your pattern [also matches](http://regexstorm.net/tester?p=%5e%5cd%7b3%7d%5ba-zA-Z%5d%24&i=%e0%b1%a6%e1%a7%97%e0%b5%adA) `string Case1 = "౦᧗൭A";`. So, "*`\d` is shorthand for `[0-9]`*" is not correct in .NET regex context. – Wiktor Stribiżew Jan 22 '21 at 09:20
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