Regular Expression For Alphanumeric String With At Least One Alphabet Or Atleast One Numeric In The String

Question

To test one alphanumeric string we usually use the regular expression "^[a-zA-Z0-9_]*$" (or most preferably "^\w+$" for C#). But this regex accepts numeric only strings or alphabet only strings, like "12345678" or "asdfgth".

I need one regex which will accept only the alphanumeric strings that have at-least one alphabet and one number. That is to say by the regex "ar56ji" will be one of the correct strings, not the previously said strings.

Thanks in advance.

Answer 1

This should do it:

if (Regex.IsMatch(subjectString, @"
    # Match string having one letter and one digit (min).
    \A                        # Anchor to start of string.
      (?=[^0-9]*[0-9])        # at least one number and
      (?=[^A-Za-z]*[A-Za-z])  # at least one letter.
      \w+                     # Match string of alphanums.
    \Z                        # Anchor to end of string.
    ",
    RegexOptions.IgnorePatternWhitespace)) {
    // Successful match
} else {
    // Match attempt failed
} 

EDIT 2012-08-28 Improved efficiency of lookaheads by changing the lazy dot stars to specific greedy char classes.

Answer 2

Try this out:

"^\w*(?=\w*\d)(?=\w*[a-zA-z])\w*$"

There is a good article about it here: http://nilangshah.wordpress.com/2007/06/26/password-validation-via-regular-expression/