How to check if a string contains HTML code in ASP.NET MVC model validation?

Question

I have a model string which looks like:

bla bla bla <b>asdad</b> bla bla bla bla <u>bla</u> ...

My model:

public class MyModel {
      [RegularExpression( @"^(<\s*([^ >]+)[^>]*>.*?<\s*\/\s*\1\s*>)$", ErrorMessage = "No tag is allowed !")]
      public string Text { get; set; }
}

I tried to negate above regex ( I know that I didn't use correctly and I don't know how to do this correctly)

I want to show error when Text contains any match of HTML code, even it has no closed tag, means should occur when met:

<b> without </b>

</b> or similar

How to achieve this with regex ?

I tried that in regex101 and not working mean that any words that are not html tag are not highlighted — Snake Eyes
– Snake Eyes, Commented Feb 29, 2016 at 13:26
You'd better make this clear in the title, as well as in this post, not in the comment. That would make it a lot easier for people who are willing to help. — Quinn
– Quinn, Commented Mar 1, 2016 at 14:04

Ehsan Sajjad · Accepted Answer · 2016-02-29 13:09:38Z

5

This is the regex for that:

<(\s*[(\/?)\w+]*)

It checks for even if single closing tag is there or opening tag is there, it matches that.

DEMO here

edited Feb 29, 2016 at 13:09

answered Feb 29, 2016 at 12:51

Ehsan Sajjad

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5 Comments

Snake Eyes Over a year ago

Ok, it is possible to negate above regex?

Ehsan Sajjad Over a year ago

negate means, it should not match html tags (there should not be html tags in string)?

Snake Eyes Over a year ago

Yes, exactly...I wish, if possible, to highlight all text that are not between < and > ...

Ehsan Sajjad Over a year ago

for that you can use like: ^((?![<>]).)*$

Shawson Over a year ago

this doesn't look reliable- it would match "5 is < 10" as a piece of html

Quinn · Accepted Answer · 2016-03-01 06:03:01Z

0

The following regex matches if a model string contains no HTML tags:

^((?!\<(|\/)[a-z][a-z0-9]*>).)*$

The demo is HERE

edited Mar 1, 2016 at 6:03

answered Feb 29, 2016 at 14:17

Quinn

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1 Comment

Quinn Over a year ago

Updated regex. I misunderstood it previously.

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