Regex for testing non-whitespace-only string

Question

I have Required attribute for some strings in my view model, but that doesn't catch if user types, say, (yes, whitespace) into the text area. I need to prevent user to submit whitespace-only strings.

I am trying to use RegularExpression attribute on my view model's properties to validate the string. I've seen some answers such as Filtering "whitespace-only" strings in JavaScript or How to validate whitespaces using jquery/ajax in an MVC view but they don't seem to work properly (yes, before you ask, I am omitting leading and trailing /s if I'm taking it from Javscript to C#). The examples at the answers to those questions usually validate only against whitespace, or no whitespace at all. What I need is that I need at least some text to validate. Having some whitespace is no problem as long as I also have some non-whitespace string too.

What regex should I use (I am not good with regexes) in my attribute to validate some text that contains at least some non-whitespace text?

5 seconds worth of googling has several answers, including stackoverflow.com/a/2788151/3279876 — Sami
– Sami, Commented Feb 15, 2016 at 14:35
@Sami well, I did google for several minutes before posting. if I did find a working solution, why would I post? — Can Poyrazoğlu
– Can Poyrazoğlu, Commented Feb 15, 2016 at 14:36

thalacker · Accepted Answer · 2020-07-08 21:57:38Z

3

The Regex needed is ^(.*\S.*)$. This will allow spaces if there is another "real" character.

In an attribute it would look something like.

//using System.ComponentModel.DataAnnotations;

[Required, RegularExpression(@"^(.*\S.*)$")]
public string Name { get; set; }

I tried adding Required(AllowEmptyStrings = false) first with no success, but that is what Microsoft says to do. It didn't work for me but the Regex above did.

answered Jul 8, 2020 at 21:57

thalacker

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Ana Kochevska · Accepted Answer · 2016-02-15 14:33:50Z

-1

You can add these data-annotations to your strings:

    [Display(Name = "Email")]
    [Required(ErrorMessage = "Please enter email address !", AllowEmptyStrings = false)]
    public string Email { get; set; }

The part AllowEmptyStrings = false will prevent you from saving empty strings (like a whitespace)

answered Feb 15, 2016 at 14:33

Ana Kochevska

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2 Comments

Can Poyrazoğlu Over a year ago

it doesn't work. added it, typed some space, and it validated, where it shouldn't.

Ana Kochevska Over a year ago

Then [RegularExpression(@"^[^\s\,]+$", ErrorMessage = "Email Can't Have Spaces")]

neuhaus · Accepted Answer · 2016-02-15 14:34:21Z

-1

the regular expression ^\s+$ matches strings that consist only of whitespace.

the regular expression \S matches strings that contain some non-whitespace.

answered Feb 15, 2016 at 14:34

neuhaus

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2 Comments

Simon Morgan Over a year ago

\S, when used with the RegularExpression attribute, won't allow a string with whitespace, even if it has non-whitespace characters.

neuhaus Over a year ago

You asked for a regular expression that matches "whitespace only". Duh.

Sebastian · Accepted Answer · 2016-02-15 14:43:38Z

-1

Try this expression: ^\S+$

Tested at http://regexr.com/3cq34.

answered Feb 15, 2016 at 14:43

Sebastian

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1 Comment

Can Poyrazoğlu Over a year ago

Have you even read the question? Your own example doesn't work if the text contains any space.

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