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C# - Need help with my regular expression

Hi all,

can someone help me with my regular expression. I have already read many pages about regular expressions, but I just don't seem to get it in general.

The function below need to check if the control_string is positive, contains only numbers and needs tot start with 1-9 followed by zero or more other numbers.

So "1", "12", "230" are ok, but "01", "a", "23c" etc. are wrong (all without the quotes of course). At the moment it works for the most part, but it also accepts "01".

What am I doing wrong?

I hope you guys can help me out.
public static Boolean checkIt(string control_string)
{
    Regex objNotNaturalPattern = new Regex("[^0-9]");
    Regex objNaturalPattern = new Regex("[1-9][0-9]*");
 
    return (!objNotNaturalPattern.IsMatch(control_string) && objNaturalPattern.IsMatch(control_string));
 
}

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fourice
Asked:
fourice
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1 Solution
 
ozoCommented:
^[1-9][0-9]*$
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fouriceAuthor Commented:
Thanks, it works!
Is it possible that you explain a bit how I can 'read' this pattern?
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fouriceAuthor Commented:
Works like a charm, but in my effort to understand regular expressions, I would like to know how to 'read' the pattern.
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fouriceAuthor Commented:
I forgot to ask, what was wrong with my original pattern?
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ozoCommented:
 ^                        the beginning of the string
----------------------------------------------------------------------
  [1-9]                    any character of: '1' to '9'
----------------------------------------------------------------------
  [0-9]*                   any character of: '0' to '9' (0 or more
                           times (matching the most amount possible))
----------------------------------------------------------------------
  $                        before an optional \n, and the end of the
                           string

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