How to count sets of specific characters in a string

Question

Basically, I want to count sets of specific characters in a string. In other words I need to count all Letters and Numbers, and nothing else. But I cant seem to find the right (regex) syntax. Here's what i have ...

public double AlphaNumericCount(string s)
{
    double count = Regex.Matches(s, "[A-Z].[a-z].[0-9]").Count;
        return count;
}

I've been looking around, but cant seem to find anything that allows more than one set of characters. Again, I'm not sure on the syntax maybe it should be "[A-Z]/[a-z]/[0-9]" or something. Anywho, go easy on me - its my first day using Regex.

Thanks.

Bobson · Accepted Answer · 2012-12-19 21:32:22Z

5

Regular Expression Cheat Sheet

Expresso Regular Expression tool

[A-Z].[a-z].[0-9] will match any capital letter ([A-Z]), followed by any character (.), followed by any lower case letter ([a-z]), followed by any character (.), followed by any number ([0-9]).

What you want to match on any letter or number is [A-Za-z0-9].

answered Dec 19, 2012 at 21:32

Bobson

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Comments

Will · Accepted Answer · 2012-12-19 21:37:09Z

4

If the use of regular expressions is not required, there is an easy, alternate solution:

return s.ToCharArray().Count(c => Char.IsNumber(c) || Char.IsLetter(c));

answered Dec 19, 2012 at 21:37

Will

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1 Comment

Peter Duniho Over a year ago

ToCharArray() is not necessary here. string already implements IEnumerable<char>

MUG4N · Accepted Answer · 2012-12-19 21:29:56Z

3

Try this one:

^[a-zA-Z0-9]+$

see: regexlib.com

answered Dec 19, 2012 at 21:29

MUG4N

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Comments

keyboardP · Accepted Answer · 2012-12-19 21:31:53Z

3

If you want to avoid regular expressions, you can simply iterate through the characters in the string and check if they're a letter or digit using Char.IsLetterOrDigit.

public int AlphaNumericCount(string s)
{
    int count = 0;

    for(int i = 0; i < s.Length; i++)
    {
       if(Char.IsLetterOrDigit(s[i])) 
          count++;
    }

    return count;
}

answered Dec 19, 2012 at 21:31

keyboardP

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1 Comment

keyboardP Over a year ago

No problem. Regex might look neater but, depending on the length of the string/number of calls, they may be slower.

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