Regular Expression

Question

0.00/5 (No votes)

See more:

Hello ,

I am coverting a java application into c#, I have the following regular expression check:

C#

Regex regex = new Regex("[a-zA-Z0-9_\\.-]{1,20}");
            if (!regex.IsMatch(name))
            {
                return true;
            }

Why does the string "#####llll" pass the pattern matching?
I need a pattern with following criteria

string length 1-20
contains any apha numeric character, special characters like underscore,dot,hyphen
please help...

Posted 4-Apr-10 23:57pm

sreejith_g

Updated 5-Apr-10 0:13am

OriginalGriff

v2

Add a Solution

3 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Accepted Answer · 2010-04-05T00:22:00

It passes because the "llll" part of the string fullfils the criteria - the "#####" part is ignored. Try it - Add

MessageBox.Show("Matched: " + regex.Match(name));

and you will see what I mean.

You could try:

Regex regex = new Regex("^[a-zA-Z0-9_\\.-]{1,20}");
            if (!regex.IsMatch(name))
            {
                return true;
            }

which forces the match to be at the beginning of the string.

It may be worth your while to get a copy of Expresso - it examines and generates Regular expressions - and its free!

J a a n s · Accepted Answer · 2010-04-05T00:26:00

Solution 5

The regular expression should be some thing like this ^[a-zA-Z0-9_\\.-]{1,20}$ Otherwise it will find the part of the string which is matching.

Posted 5-Apr-10 0:26am

J a a n s

OriginalGriff · Accepted Answer · 2010-04-05T00:05:00

Solution 1

I see nothing obvious - what error are you getting? Is there a message? Exception?

Posted 5-Apr-10 0:05am

OriginalGriff

Comments

Toli Cuturicu 8-Sep-10 12:09pm

Reason for my vote of 2
See the other answers.