How to make a regex match case insensitive?

Question

I have following regular expression for postal code of Canada.

^[ABCEGHJKLMNPRSTVXY]{1}\d{1}[A-Z]{1} *\d{1}[A-Z]{1}\d{1}$

It is working fine but accepts only Capital letters. I want it work for both capital and small letters.

Just type in the lowercase letters or make your regex case-insensitive. — Blender, Aug 15 '12 at 07:29
language is C# but your expression contains [A-Ya-y] which is not correct because canada post code can not contain letters D, F, I, O, Q, or U — khurram, Aug 15 '12 at 07:41
You should probably also allow - as the separator. It's not technically correct, but it's easy enough to change to a space if you care. — Steven Fisher, Aug 15 '12 at 15:28
If you are using .net regex object then try using stema's answer. — Vaibhav Jain, Aug 19 '12 at 13:54
Possible duplicate of [Case insensitive Regex without using RegexOptions enumeration](https://stackoverflow.com/questions/2439965/case-insensitive-regex-without-using-regexoptions-enumeration) — juFo, Feb 20 '18 at 08:13

stema · Accepted Answer · 2014-03-03T08:33:03.263

144

Just use the option IgnoreCase, see .NET regular Expression Options

So your regex creation could look like this

Regex r = new Regex(@"^[ABCEGHJKLMNPRSTVXY]\d[A-Z] *\d[A-Z]\d$", RegexOptions.IgnoreCase);

I removed also all your {1} because it is superfluous. Every item is per default matched once, no need to state this explicitly.

The other possibility would be to use inline modifiers, when you are not able to set it on the object.

^(?i)[ABCEGHJKLMNPRSTVXY]\d[A-Z] *\d[A-Z]\d$

edited Mar 03 '14 at 08:33

answered Aug 15 '12 at 07:59

stema

9

Upped the score for the mention of "(?i)" prefix that came in handy when declaring a regular expression in the [RegularExpression("regex-string")] validation attribute in MVC. Thank you! – timmi4sa Jan 18 '21 at 21:58

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