CODEWITHSUNDEEP
regexvb.net
faedra
faedra

Reputation: 63

Period in .Net 3.5 Regex.IsMatch

I came across this regular expression in vb.net 3.5 code:

Regex.IsMatch(strString, "^[\w\s.+'\-\(\)\/\,\&\#]+$")

What is really confusing me is the ".+" part. I was under the impression that the period means any character and the plus sign means one or more. Following this, I feel like this regular expression should allow anything! But it doesn't, so I must be misunderstanding something. In testing it, it seems like the period and the plus sign are being taken as literals.

Could somebody help explain this to me?

Thanks!

Upvotes: 2

Views: 279

Answers (3)

NineBerry
NineBerry

Reputation: 28509

Within the square parenthesis, dot and plus don't have their special meaning. The square brackets define a "character class". It does not contain a string but a set of characters allowed at this position.

So the expression [\w\s.+'-()/\,\&#] creates a character class of letters, digits, underscore, spaces, dots, pluses, single quotes, minuses, opening round brackets, closing round brackets, slashes, commas, ampersands and hashmarks.

The + behind the square parenthesis means you expect one or more characters of this character class.

Upvotes: 0

Steven Doggart
Steven Doggart

Reputation: 43743

The issue is that all of those characters are enclosed in a [character-group]. The escaping rules are different in character-groups than they are elsewhere in a RegEx expression. For instance, according to the MSDN documentation, \b inside a character-group means a backspace character whereas, outside of a character-group, it is an anchor that matches a word boundary.

According to the Regular-Expressions.info documentation:

In most regex flavors, the only special characters or metacharacters inside a character class are the closing bracket (]), the backslash (), the caret (^), and the hyphen (-). The usual metacharacters are normal characters inside a character class, and do not need to be escaped by a backslash.

Therefore, in your example RegEx expression, it looks for any one of the characters in that bracketed list, including either the literal . or + character. If you think about it, it wouldn't make any sense to use a . to mean "any character" inside of a character-group. Doing so would make the group, itself, moot. And certainly, using the + character to mean "one or more times" inside of a character-group really makes no sense.

Upvotes: 2

Victor Bocharsky
Victor Bocharsky

Reputation: 12306

.+ is mean any symbol in an amount of one or more. Maybe you need to escape dot like \.+?

Upvotes: 0

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