#970 – Checking for Valid Characters in a String

You can use a regular expression to check a string to see if the string contains only characters within a specified set of characters.

For example, to check whether a string is limited to a single line containing only alphabetic characters (e.g. a..z, A..Z), you can use the regular expression shown below.

        private bool IsAlphabetic(string s)
        {
            Regex r = new Regex(@"^[a-zA-Z]+$");

            return r.IsMatch(s);
        }

The regular expression defines a pattern and the IsMatch method checks the string to see if it matches the pattern.  You can read the regular expression as follows:

  • ^ – start of the string
  • [a..zA..Z] – single character that is a lowercase or uppercase letter
  • + – repeat previous item one or more times (alphabetic character)
  • $ – end of the string

A string will therefore match if it is a single line of text containing at least one alphabetic character and is limited to alphabetic characters.

946-001

946-002

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About Sean
Software developer in the Twin Cities area, passionate about software development and sailing.

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