Regular Expression required!!

Morpheus

writing code to validate a new users password in ASP.NET and c#

not used to Regex's at all to be honest, im currently checking this

[a-zA-Z0-9]

but it only ensures that the string contains alpha OR numeric values... can anyone enlighten me as to how to ensure a string is alphanumeric but MUST HAVE a numeric value in it.

eg i want to ensure that all passwords are in this format....

"password1"

"mypass3ord"

"password34"

"elephant50"

"elrond1234"

regards
Morph :eek:

zoro

Is this any use??

http://www.experts-exchange.com/Web/Web_Languages/JavaScript/Q_21059770.html

zoro

Or this?
http://www.breakingpar.com/bkp/home.nsf/Doc?OpenNavigator&U=87256B280015193F87256C4F005D3717

Try this google link
http://www.google.ie/search?q=regex+password+check&hl=en&lr=&ie=UTF-8&start=10&sa=N

I dont' know enough about Regex, but google does

Haruspex

This site should provide you with a solution:
Reg Ex Lib
Expressions can be tested for accuracy also.

PhilH

You want to chech this, but...

The pattern you give [a-zA-Z0-9] will match a single character which is an letter or a number

so this pattern matches


a - true
F - true
9 - true
a9 - false, this is two characters long, not 1
bm - false, this is two characters long, not 1


The pattern [a-zA-Z0-9]* will match a sequence of zero or more letter/numbers.


a9 - true
b_m - false, as one of the characters is not a letter/number


I think the easiest way for you to handle your situation is to use more than one pattern. I would suggest at least three...

[a-zA-Z0-9]* - a sequence of zero or more letters or numbers
If the password doesn't match this it must contain illegal characters.

[^0-9]* - a sequence of zero or more characters that are not digits
If the password matches this then it has no digits in it.

[^a-zA-Z]* - a sequence of zero or more characters that are not letters
If the password matches this then it has no letteres in it (which is probably also a problem for you)

You will probably also want to check that the password is above some minimum length.

Hope that's of some use to you. Please check the patterns I gave you, they work for me but I don't know what regular expression engine you are using. I was just using Java, with the following code...

Pattern p = Pattern.compile(_pattern);
Matcher m = p.matcher(_text);
System.out.println(m.matches());

PHiL

Morpheus

Wrote the following method that takes in the test string and returns true or false

but it failed

sample strnigs passed in were....

password1 = should return true....
password = should fail cos theres no numeric value in it
pass2222word = should return true

all failed

public bool IsAlphaNumeric(string strToCheck)
{
		
    Regex objAlphaNumericPattern=new Regex("^(?=.*\\d).{4,8}$") ;
    return !objAlphaNumericPattern.IsMatch(strToCheck,0) ;
}

anyone any more ideas???

Kev

it failed because password1 and pass2222word are longer than 8 characters

Spunj

Heres a quick stab at it:

([a-zA-z]+[0-9]+[a-zA-z]?)|([a-zA-z]+[0-9]+)|([0-9]+[a-zA-z]+\w?)

you didnt mention any specific lengths of password so that will validate short ones (2 characters).

Morpheus

This is f*cked up...

heres the code im using to even just check that a string is alpha only...... [a-z]

private void btnAlphaNumeric_Click(object sender, System.EventArgs e)
{
  	if(IsAlphaNumeric(txtAlphaNumeric.Text) == true)
	{
		lblTrueFalse.Text = "True" ;
	}
	else
		lblTrueFalse.Text = "False" ;
	}
}

public bool IsAlphaNumeric(string strToCheck)
{
	Regex objAlphaNumericPattern=new Regex("[a-z]") ;
	Debug.Write(objAlphaNumericPattern.ToString()) ;
	return !objAlphaNumericPattern.IsMatch(strToCheck) ;
}

now if i type in "abcdef" im getting back false and if i type in "123456" i get true ???

WHAT THE F*CK IS GOING ON??? ANY IDEAS???

PhilH

Are you sure you want that exclamation mark in front of your return value?

Surely IsMatch is giving you a true if strToCheck matches the expression [a-z]. Your are flipping this boolean value before passing it back to the caller.

Assuming that though, your example of "abcdef" is causing IsMatch to return 'true'. This is a bit worrying because "abcdef" is not a single character in the range 'a' to 'z'. It might be that the IsMatch is actually checking whether or not strToCheck *contains* a match for your regular expression, rather than checking whether or not it *is* a match. If so, the method is appallingly named, but you'll have to check .NET documentation for details.

PHiL

Morpheus

WOW... flash of inspiration (and some more research and testing)

IsMatch() searches for ANY single match possible, not any non matches so without the exclamation mark we would be returning any "matches".

However im trying to catch any patterns that DONT match, therefore i need the exclamation mark, so that checking a string of "111" against the range a-z would return true because 111 IS a NON match.

therefore my current regex of ^(?![0-9]{6})[0-9a-zA-Z]{6}$ substituted into the above code snippet returns the following...

passs1 = false (no non matches found)

pas1 = true (non match because its less than 6 chars long)

pa1 = true (as above)

111 = true (less than 6 and no alphas)

1pass2 = false (no non matches)

so false is true and true is false )

thanks for all the help guys!

PhilH

Looking at your regular expression, my first reaction is 'jesus, that looks complicated'. You should be able to make much simpler (and therefore very much easier to understand and maintain) code.

You have a method that tells you is there is a match for regular expression 'x' in string 's' (terrible naming by the .NET guys, calling it IsMatch, but what can you do?).

Do four checks, not one

1) if there is a match for '[^0-9A-Za-z]' in 's' then 's' contains some character that is not a letter or digit, so reject it

2) if there is no match for '[0-9]' in 's' then 's' doesn't contain a digit, so reject it

3) if there is no match for '[A-Za-z]' in 's' then 's' doesn't contain a letter, so reject it

4) check the length of 's' to make sure that it is long enough for your needs

From that, I really think you're pretty damn close to having your problem solved.

It *may* be possible to right a single regular expression that would perform the check that you need (I am not at all confident that this is the case, but maybe it's possible). However, the IsMatch function you are relying on would only go as far as telling you that 's' *contains* a valid password, not that it *is* one. So it would say '--P4ssw0rd::' is valid, because 'P4ssw0rd' is fine and is in the middle there.

So if I were you, I would cut my losses now and not bother looking for that possible one-regular-expression test, and code up something simple like the steps above.

PHiL

Morpheus

i did it even more simple...

public bool ValidatePassword(string pwd)
{
	int num = 0 ;
	int chr = 0 ;

	// Ensure the password is 8 or more characters in length
	if (pwd.Length >= 8)
	{
		foreach(char x in pwd)
		{
			// check at least one character is a number
			if(char.IsNumber(x) )
			{
				num++ ;
			}
			// check at least one character is a letter (a-z)
			if(char.IsLetter(x) )
			{
				chr++ ;
			}
		}
		// check if the password contains both numeric and alpha characters
		if(chr > 0 && num > 0)
			return true ;
		else
			return false ;
	}

	// password is invalid
	else
		return false ;
}

Were not worried about underscores, etc, just 8 or more chars containing letters and at least one number.

No RegEx's

Morpheus

ok i need a regualr expression for irish phone numbers

to take the following form...

area code optionally enclosed in brackets eg (041), containing 1-3 numbers
^\(?\d{1,3}\)?

followed by a space, a dash or no space or dash

^\(?\d{1,3}\)?\s?|-

followed by 5 - 7 numbers making the rest of the telephone number

^\(?\d{1,3}\)?\s?|-\d{5,7}$


whats wrong though? i cant get it to work???

any ideas?

Kev

^\(?\d{1,3}\)?[\s-]?\d{5,7}$

also what was wrong with ^(?=.*\d).{4,8}$ for your first problem