RegEx for ABC_XYZ_PPQRST-AA

Question

I need to create a regex to test below kind of data,

xxx_yyy_zzz-aaa

I am able to verify the first two _ underscore, but unable to append the - hyphens.

@"[a-zA-Z0-9]_[a-zA-Z0-9]_[a-zA-Z0-9]s/[^-][a-zA-Z0-9]"

I am using c#. the number of characters above are just for an example

`[a-zA-Z0-9]` matches a *single* character. Add `{3}` to match exactly 3 — Hans Keﬆing, Feb 21 '18 at 08:35
I had tried with \ i.e. escape. I'm not sure why its not working — Pawan Dubey, Feb 21 '18 at 08:37
@PawanDubey, it seems like you are missing the basic here. May I recommend you to read [this](https://regexone.com/) step by step tutorial then to pratice and debug your regex on a [online regex debugger](https://regex101.com/) like this one? — Drag and Drop, Feb 21 '18 at 08:41

score 2 · Accepted Answer · answered Feb 21 '18 at 09:23

The xxx_yyy_zzz-aaa string implies that the format is {alphanum}_{alphanum}_{alphanum}-{alphanum}. The pattern for the {alphanum} part has already been written by you.

Next, you want to quantify each alphanumeric part since just [A-Za-z0-9] matches a single alphanum char. Use + to match 1 or more occurrences, or {3} to match only 3, or {3,} to match 3 or more.

That is not all, since you expect the whole string to match the pattern. Hence, you need anchors, ^ to match the start of string and $ (or \z) to match the end of string.

Thus, I'd recommend

@"^[a-zA-Z0-9]+_[a-zA-Z0-9]+_[a-zA-Z0-9]+-[a-zA-Z0-9]+\z"

See the regex demo.

RegEx for ABC_XYZ_PPQRST-AA

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