Regular Expression in .NET

Question

I should write a regex pattern in c# that checks for input string whether it conains certain characters and does not conain another characters, for example: I want that the string contain only a-z, not contain (d,b) and the length of all the string longer than 5, I write "[a-z]{5,}", how can I avoid that the input contain d and b?

Additional question: Can I have option to condition in the regex, in other words if whichever boolian var equals true check somthing and if it equals false not check it?

Thanks

Spudley · Accepted Answer · 2011-04-12 10:25:50Z

4

simple regex:

/[ace-z]{5}/

matches five occurrences of: characters 'a', 'c', or any character between 'e' and 'z'.

answered Apr 12, 2011 at 10:25

Spudley

169k39 gold badges240 silver badges309 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

WraithNath · Accepted Answer · 2011-04-12 10:44:49Z

1

A useful regex resource I always use is:

http://regexlib.com/

Helped me out many times.

answered Apr 12, 2011 at 10:44

WraithNath

18.1k10 gold badges59 silver badges84 bronze badges

Comments

Felice Pollano · Accepted Answer · 2011-04-12 10:59:30Z

1

For the first question, why not simply try this: [ace-z]{5,} ? For the second option, can't you format the regex string in some way based on the boolean variable before executing it ? Or, if you want programmatically exclude some chars, you can create programmatically the regex by expliciting all the chars [abcdefgh....] without the exclusion.

edited Apr 12, 2011 at 10:59

answered Apr 12, 2011 at 10:24

Felice Pollano

33.4k10 gold badges77 silver badges126 bronze badges

3 Comments

RRR Over a year ago

I only write an example in the Q, and I cannot write explicitly every time that I should a range of characters without several charcters in the range.

Felice Pollano Over a year ago

@RRR so your excluded carachter changes ? So why not generate the regex extended: [abcdefg...] programmatically excluding the needed chars ?

RRR Over a year ago

if I dont have any option I do that, but if I can write expression that do that for me - I prefer, when I write [abcdefgh....], I don't exhaust the possibilities of Regex object

niksvp · Accepted Answer · 2011-04-12 11:05:38Z

1

if you want to skip d and b

[ace-z]{5,}

And yes you can have a boolean check using isMatch method of Regex class

 Regex regex = new Regex("^[ace-z]{5,}$");
    if (regex.IsMatch(textBox1.Text))
    {
        errorProvider1.SetError(textBox1, String.Empty);
    }
    else
    {
        errorProvider1.SetError(textBox1, 
              "Invalid entry");
    }

Source

edited Apr 12, 2011 at 11:05

answered Apr 12, 2011 at 10:20

niksvp

5,5512 gold badges28 silver badges43 bronze badges

5 Comments

Tim Pietzcker Over a year ago

Drop the commas in your regex.

niksvp Over a year ago

@Tim Pietzcker - yeah, Thanks

RRR Over a year ago

its not work, Regex.isMatch return true for this string "aaaaab"!

Tim Pietzcker Over a year ago

Add a comma to your regex :) ^[ace-z]{5,}$ to allow for more than 5 characters. Then this is the best solution.

RRR Over a year ago

its not work, and anyway I prefer a expression that avoid insert certain charcters, not write explicitly, if it possible. thanks for the want to help!

Collectives™ on Stack Overflow

Regular Expression in .NET

4 Answers 4

Comments

Comments

3 Comments

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

3 Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related