Negating specific characters in regex

Question

How can I block white space in textbox entries?

I tried this but it is not working:

  [RegularExpression(@"/^\s/", ErrorMessage = "white space is not allowed in username")]
  public string UserName { get; set; }

'^' negation should not allow white space in text but it does not allow me to enter any text in field. Any help?

Do you need to use regex for this? Try to find a space and if you find one, prevent from getting further. — Jerry, Dec 27 '13 at 12:59
i am working with Data Annotations, so i need to stick with regex — A.T., Dec 27 '13 at 13:01

score 2 · Accepted Answer · answered Dec 27 '13 at 12:58

2

Use \S (which is negation of \s = non-whitespace character):

@"^\S+$"

If empty string is allowed, replace + with *:

@"^\S*$"

answered Dec 27 '13 at 12:58

falsetru

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There's no `/` delimiter in .net regex – Anirudha Dec 27 '13 at 13:01
@Anirudh, Thank you for comment. I fixed it according to your comment. – falsetru Dec 27 '13 at 13:01
@Arun, it's likely the `^` and `$` terminators. Remove them and it will probably yield the results you're looking for. – Mike Perrenoud Dec 27 '13 at 13:06
i tried @"/\S+/" but still not working? i am keep getting validation for non-white space string – A.T. Dec 27 '13 at 13:12

score 2 · Answer 2 · edited May 23 '17 at 12:25

Just saw the comment you said "you need to work with DataAnnotation", here is the way to do it without Regex

public class WhiteSpaceCheckerAttribute : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        var strValue = value as string;
        return strValue != null && !strValue.Contains(" ");
    }
}

usage

[WhiteSpaceChecker(ErrorMessage = "white space is not allowed in username")]
public string UserName { get; set; }

This doesn't cover client side validation which you can easily implement. Following link should help you with that concept Client-side custom data annotation validation

score 2 · Answer 3 · answered Dec 27 '13 at 14:34

2

^ works as "negation" only inside character classes, e.g. [^ ] means any character except space. When used outside of [], ^ means "at the beginnign of the string. So your original RE says "A space at the start of the string" - almost exactly the opposite to what you want.

I am not the familiar with specifics of C# REs, but from the rest of the answers, the RE you want is probably ^\S+$: 1 or more non-space characters between beginning and end of the string.

answered Dec 27 '13 at 14:34

i am not familiar with Regex, my requirement is to not allow white space in string, all other characters and symbols are allowed – A.T. Dec 27 '13 at 14:47
This answer has been added to the [Stack Overflow Regular Expression FAQ](http://stackoverflow.com/a/22944075/2736496), under "Character Classes". – aliteralmind Apr 10 '14 at 00:16

score 0 · Answer 4 · answered Jun 09 '16 at 11:15

0

You can do this without RegEx. By adding this code in the KeyPress Event of your textbox.

private void textBox1_KeyPress(object sender, KeyPressEventArgs e)
{
    e.Handled = e.KeyChar == ' ';
}

answered Jun 09 '16 at 11:15

Tassisto

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Negating specific characters in regex

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