Regex.IsMatch in C#

Question

I know this is a very basic question, but I was unable to find an answer. I am trying to use the function validateRegexData in C#. All I am doing is to validate something that's supposed to be alphanumeric. So an example I saw had this:

Regex.IsMatch(inputString, "^[a-zA-Z0-9]+$")

I get only PART of the second parameter: why is there a "+$" sign? Believe me, I tried reading the documentation for an hour, and still didn't get why the parameter starts with "^" and ends with "+$". I saw somewhere that $ indicates that everything up until \n is fair game as validation (meaning inside the first parameter).. but that still doesn't explain the + sign, and I'm not even sure if what I read applies here. Thank you so much in advance.

Not that it makes a difference, but it'll be used in SSIS Sorry - I had used the wrong name, I meant to say "Regex.IsMatch" !!

This was me on first day of learning regex. – Mar 09 '16 at 18:02 — , Mar 09 '16 at 18:02
The "duplicate" isn't really what I'm asking here. – LearnByReading Mar 10 '16 at 17:15 — LearnByReading, Mar 10 '16 at 17:15

score 3 · Accepted Answer · edited Mar 09 '16 at 18:04

3

This is quite simple:

^[a-zA-Z0-9]+$
^                 <= Start of line
 [a-zA-Z0-9]      <= Any character in the range a to z or A to Z or 0 to 9
            +     <= Repeat previous pattern (here: [a-zA-Z0-9]) one or more time
             $    <= End of line

If you need more explanations in the future about regexes, you can get it explained on Regex101 for example

edited Mar 09 '16 at 18:04

user4003407

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answered Mar 09 '16 at 17:58

Thomas Ayoub

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Thanks for your answer. But why do I need the +? Why does it need to repeat the previous pattern?? – LearnByReading Mar 09 '16 at 19:22
@LearnByReading you don't *need* it. I allow you to have a string of a length from 1 to ∞ – Thomas Ayoub Mar 09 '16 at 19:29

Regex.IsMatch in C#

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