C# ASP.NET application Regular expression

Question

For a C#, ASP.NET application - This should be simple, but I can't figure out this regular expression, I need a list of strings that a text box can not submit as a value, and I have to ignore the case.

Example - No matter the capitalization, I need my regular expression to reject the following strings - abc, def, ghi

I can't even get the regex to reject one of them. I tried the following manner -

[RegularExpression(@"(\W|^)(?i)!ABC(?-i)(\W|$)", ErrorMessage = "REJECTED!")]
public string Letters { get; set; }

That does not work! It seems to reject everything. Anyone know what it should look like? How can I reject all of them?

Thanks for any help can provide!

Constantino Tsarouhas · Accepted Answer · 2013-02-15 14:51:04Z

2

Quick and dirty, but give this a try (assuming I understand the problem correctly!)

^(?i)(?!(ABC|DEF|GHI)(?-i)).*$

edited Feb 15, 2013 at 14:51

Constantino Tsarouhas

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answered Feb 14, 2013 at 21:38

David W

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Markus Meyer · Accepted Answer · 2013-02-14 21:57:33Z

2

In standard regex syntax this would be ^(?!abc$)(?!def$).*

answered Feb 14, 2013 at 21:57

Markus Meyer

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Jason · Accepted Answer · 2013-02-14 21:58:01Z

2

This will detect abc, def, and ghi

(?i)(abc|def|ghi)

enclose in ^ and $ to only match those and nothing else (e.g. won't match wxabcyz)

^(?i)(abc|def|ghi)$

finally, if you want to match something like "This is some abc random text" and reject it, do this

(?i)\b(abc|def|ghi)\b

answered Feb 14, 2013 at 21:58

Jason

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Olaf Dietsche · Accepted Answer · 2013-02-14 21:59:23Z

2

If you want to ignore just strings, use this

^(?i)(?!.*(?:abc|def|ghi))

If you want to ignore words, use word boundaries around the pattern

^(?i)(?!.*\b(?:abc|def|ghi)\b)

edited Feb 14, 2013 at 21:59

answered Feb 14, 2013 at 21:39

Olaf Dietsche

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Terrance · Accepted Answer · 2013-02-14 21:59:36Z

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^((?!abc)|(?!def)|(?!ghi).)*$

Thats about it.

Btw I'd recommend you play around with something like the following resources you aren't already.

regex pal and regular-expressions.info

answered Feb 14, 2013 at 21:59

Terrance

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Siby Sunny · Accepted Answer · 2016-11-16 15:20:17Z

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^(?i)(?!(ABC|DEF|GHI)(?-i)).*$

answered Nov 16, 2016 at 15:20

Siby Sunny

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