Reg Ex negation

Question

I am using .Net. I want to match last name which has charecters other than a-z, A-Z, space and single quote and len of charecters should not be between 1-40 . The string that has to be matched is a XML look like this <FirstName>SomeName</FirstName><LastName>SomeLastName</LastName><Address1>Addre1</Address1>

I wrote regualr expression but that is matching only [a-zA-Z'.\s]{1,40} <LastName>[a-zA-Z'.\s]{1,40}</LastName> EDIT:LastName tag is missed. But I want to get negation of this expression. Is that possible or should I take different approach?

Answer 1

You can have negated character classes. [^abc] matches any character that is NOT a, b, or c. For your case, you might want [^a-zA-Z'.\s]{1,40}

Since your data is in XML tags, you will probably want to extract from those first. XML and regular expressions don't always mix well.

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If you absolutely must deal with the XML tags in the regex you could try something like this:

<FirstName>([^a-zA-Z'.\s]{1,40})</FirstName><LastName>([^a-zA-Z'.\s]{1,40})</LastName>

Capture group 1 will be the first name, capture group 2 will be the last name.

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Misread original question, if you want to match strings MORE than 40 characters, the length should be {41,} not {1,40}. This will ensure you only match on strings with more than 40 characters.

Answer 2

Hi,

The negation character is "^". So your expression would read like the following:

[^a-zA-Z'\S]{1,40}.

Here is a link to Microsoft's site about negation.

Enjoy

Answer 3

try this pattern

"<LastName>([^a-zA-Z'\s])|(.{41,})</LastName>"

Answer 4

[EDIT] - Removed other stuff. Here's something that worked for all conditions (including empty) in my tests, including have the XML in the tested string.

/^(<LastName><\/LastName>)|(<LastName>.*[^a-zA-Z'\s]+.*<\/LastName>)|(<LastName>(.{41,})<\/LastName>)$/

Answer 5

You seem to want to know how to negate a pattern match without using some "not"-type logic in the language, but placing it in the pattern match itself.

If that's what you really mean, all you need to do is convert your "regex" into "^(?:(?!regex).)*$".

The first is true of any string that contains "regex", and the second is true of any string that does not contain "regex".

I suppose if you want to be mindful of multilined input strings, that should be "\A(?:(?!regex)(?s).)*\z" just to be super-careful.