Strange behavior with ^ character

Asked Jan 14 '16 at 10:22

Active Nov 19 '17 at 14:52

Viewed 58 times

I'm trying to make create a simple RegEx to test whether a string is a valid variable name (starts with a letter or _, followed by more of these or digits).

Here's what I'm trying to do:

bool match = Regex.IsMatch(@"abc",@"^[a-zA-z_][a-zA-z_0-9]*$"); // TRUE as expected
bool match = Regex.IsMatch(@"=abc",@"^[a-zA-z_][a-zA-z_0-9]*$"); // FALSE as expected
bool match = Regex.IsMatch(@"0abc",@"^[a-zA-z_][a-zA-z_0-9]*$"); // FALSE as expected

Seems to work fine. But:

bool match = Regex.IsMatch(@"^abc",@"^[a-zA-z_][a-zA-z_0-9]*$"); // TRUE. WHY?!

How is it possible that =abc does not match but ^abc does? It almost seems like the caret somehow breaks the RegEx engine. But that can't be the case. What's wrong with my RegEx?

edited Jan 14 '16 at 10:23

Tushar

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asked Jan 14 '16 at 10:22

amida

1

What a bizarre 2 downvotes - your question is perfectly clear. – Jamiec Jan 14 '16 at 10:26
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To actually answer your question: you have a typo, and the regex should read: `@"^[a-zA-z_][a-zA-Z_0-9]*$"` – sloth Jan 14 '16 at 10:31
It is perfectly clear that the typo is in `A-z`. Use `A-Z` or the `A-z` range will match more than you need. – Wiktor Stribiżew Jan 14 '16 at 10:36
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Oh, I found a much better duplicate source - [I answered the same question some months ago](http://stackoverflow.com/a/29771926/3832970). – Wiktor Stribiżew Jan 14 '16 at 11:23

Strange behavior with ^ character

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