Password validation - RegExp

[r3g]

Hi,

Simple RegExp request here, well I think it's simple. I'm looking for RegExp pattern that will match a string which contains at least 5 alphabetic characters [a-zA-Z] (not necessarily in sequence).

e.g:
wordword - would match
word121word - would match
w1w1w1w1w1 - would match
w1w1w1 - no match

Thanks

 

[crazyboybert]

Im sure using some clever stuff like lookahead assertions etc you could just write and expression to test for this but another way to do it would be...

bool TestString(string s){
  RegEx r = new RegEx("[a-zA-Z]");
  MatchCollection mc = r.Matches(s);
  if(mc.Count >= 5) return true;
  else return false;
}

Rob

i'm a boy, called Bert, and I may not be crazy, but if i'm not the rest of you are...

 

[cappmgr]

Same as cbb just added the length check in the regex in case you also want to use it in a rev in the aspx
[a-zA-Z]{5,20}
just states must be at least 5 and no more than 20.
Marty

 

[crazyboybert]

Marty: Wouldn't the above only match instances of between 5 and 20 (inclusive) consecutive alpha characters so would fail to match

http://www11ww

as required? Thats why I went for testing MatchCollection.Count instead as the basic RegEx [a-zA-Z] matches one instance of an alpha character so if there are 5 or more matches in the collection you know there were at least 5 alpha characters.

I'm sure you can write an expression which handles the whole job and i'm pretty certain that forward (look-ahead) assertions are the trick to it. If this for a RegularExpressionValidator then the above code in a CustomValidator would do the trick in the meantime.

One downside of this approash though is there is no way to disallow other characters from the string without running a seperate expression to validate allowed characters. just depends on your requirements and how much you want to try for the truly eleganty solution ;-)

I've got 5 mins so I'll have a go at the expression anyway.

Rob

i'm a boy, called Bert, and I may not be crazy, but if i'm not the rest of you are...

 

[crazyboybert]

Lol - its actually much simpler than all that over complicated stuff I rambled about before. Just check for an alpha char followed by any number of optional numeric chars a minimum of 5 times like this

([a-zA-Z]\d?){5,}

Simple

I tested it against all of the conditions you provided above and a few more and it seems ok. this is easily extend to allow other characters as well but wouldn't allow invalid chars.

Rob

i'm a boy, called Bert, and I may not be crazy, but if i'm not the rest of you are...

 

[cappmgr]

Rob,
Thank you very much. My bad, I did not read it close enough and worse I did not test it.
Marty