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

To test one alphanumeric string we usually use the regular expression 开发者_运维问答"^[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.

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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.

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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/

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This should work:

"^[a-zA-Z0-9_]*([a-zA-Z][0-9]|[0-9][a-zA-Z])[a-zA-Z0-9_]*$"

This will match:

<zero-or-more-stuff>
EITHER <letter-followed-by-digit> OR <digit-followed-by-letter>
<zero-or-more-stuff>

By ensuring you have either a digit followed by letter or a letter followed by digit, you are enforcing the requirement to have at least one digit and at least one letter. Note that I've left out the _ above, because it wasn't clear whether you would accept that as a letter, a digit, or neither.

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Try this one ^([a-zA-z]+[0-9][a-zA-Z0-9]*)|([0-9]+[a-zA-z][a-zA-Z0-9]*)$

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Simple is better. If you had a hard time writing it originally, you're (or some other poor sap) is going to have a hard time maintaining it or modifying it. (And I think that I see some possible holes in the approaches listed above.)

using System.Text.RegularExpressions;

boolean IsGoodPassword(string pwd){
    int minPwdLen = 8;
    int maxPwdLen = 12;
    boolean allowableChars = false;
    boolean oneLetterOneNumber = false;
    boolean goodLength = false;

    string allowedCharsPattern = "^[a-z0-9]*$";

    //Does it pass the test for containing only allowed chars?
    allowableChars = Regex.IsMatch(pwd, allowedCharsPattern , RegexOptions.IgnoreCase));

    //Does it contain at least one # and one letter?
    oneLetterOneNumber = Regex.IsMatch(pwd, "[0-9]")) && Regex.IsMatch(pwd, "[a-z]", RegularExpressions.IgnoreCase));

    //Does it pass length requirements?
    goodLength = pwd.Length >= minPwdLength && pwd.Length <= maxPwdLength;

    return allowableChars && oneLetterOneNumber && goodLength;
}