Simple and Tested Online Regex Containing Regex Delimiters Does Not Work in C# Code

Simple and tested online regex containing regex delimiters does not work in C# code

Do not use regex delimiters:

name = Regex.Replace(name, @"\W", "");

In C#, you cannot use regex delimiters as the syntax to declare a regular expression is different from that of PHP, Perl or JavaScript or others that support <action>/<pattern>(/<substituiton>)/modifiers regex declaration.

Just to avoid terminology confusion: inline modifiers (enforcing case-insensitive search, multiline, singleline, verbose and other modes) are certainly supported and can be used instead of the corresponding RegexOptions flags (though the number of possible RegexOptions flags is higher than that of inline modifiers). Still, regex delimiters do not influence the regex pattern at all, they are just part of declaration syntax, and do not impact the pattern itself. Say, they are just kind of substitutes for ; or newline separating lines of code.

In C#, regex delimiters are not necessary and thus are not supported. Perl-style s/\W//g will be written as var replaced = Regex.Replace(str, @"\W", string.Empty);. And so on.

Regex does not work in application, yet it works on websites

Forward slashes are JavaScript's way of indicating the boundaries of a Regular Expression, much the same way that double-quotes indicate the boundaries of a string. For example, the following two expressions in JavaScript are equivalent:

/^[0-9]+([,.][0-9]{2,2})?$/.test("500,21")

new RegExp("^[0-9]+([,.][0-9]{2,2})?$").test("500,21")

Online Regex testers will often add those forward-slashes for you because they're thinking in a JavaScript context. But they're not actually part of the Regular Expression itself.

In C#, you're passing the regular expression as a string, so those slashes aren't necessary.

string value = "500,21";
bool is_valid = Regex.IsMatch(value, "^[0-9]+([,.][0-9]{2,2})?$");

Regex.IsMatch( Abcd , @ /^\S*$/ ); returns false

The / surrounding characters are delimiters for the regex itself -- for example, in javascript you can use those in place of quotes: "Abcd".match(/^\S*$/)

In C#, you must use quotes, so you can write your code simply as:

Regex.IsMatch("Abcd", @"^\S*$")

Simple and tested online regex containing regex delimiters does not work in C# code

Do not use regex delimiters:

name = Regex.Replace(name, @"\W", "");

In C#, you cannot use regex delimiters as the syntax to declare a regular expression is different from that of PHP, Perl or JavaScript or others that support <action>/<pattern>(/<substituiton>)/modifiers regex declaration.

Just to avoid terminology confusion: inline modifiers (enforcing case-insensitive search, multiline, singleline, verbose and other modes) are certainly supported and can be used instead of the corresponding RegexOptions flags (though the number of possible RegexOptions flags is higher than that of inline modifiers). Still, regex delimiters do not influence the regex pattern at all, they are just part of declaration syntax, and do not impact the pattern itself. Say, they are just kind of substitutes for ; or newline separating lines of code.

In C#, regex delimiters are not necessary and thus are not supported. Perl-style s/\W//g will be written as var replaced = Regex.Replace(str, @"\W", string.Empty);. And so on.

Get different result with the same regex pattern in C#

Use the RegexOptions.Multiline option so that ^ matches at the beginning of a line (instead of the beginning of the string). So your matching code should be like:

var sections = Regex.Matches(
    inistr, @"^\[.*\](\r|\n|\r\n)[a-zA-Z0-9_=.\r\n]*", RegexOptions.Multiline
);

Simple and tested online regex containing regex delimiters does not work in C# code

Do not use regex delimiters:

name = Regex.Replace(name, @"\W", "");

In C#, you cannot use regex delimiters as the syntax to declare a regular expression is different from that of PHP, Perl or JavaScript or others that support <action>/<pattern>(/<substituiton>)/modifiers regex declaration.

Just to avoid terminology confusion: inline modifiers (enforcing case-insensitive search, multiline, singleline, verbose and other modes) are certainly supported and can be used instead of the corresponding RegexOptions flags (though the number of possible RegexOptions flags is higher than that of inline modifiers). Still, regex delimiters do not influence the regex pattern at all, they are just part of declaration syntax, and do not impact the pattern itself. Say, they are just kind of substitutes for ; or newline separating lines of code.

In C#, regex delimiters are not necessary and thus are not supported. Perl-style s/\W//g will be written as var replaced = Regex.Replace(str, @"\W", string.Empty);. And so on.

Regex return always false c#

Just remove surrounding / from your regex, there is no need for it in .NET.

Case insensitivity can be specified using RegexOptions.IgnoreCase second argument of Regex constructor.

Regex rgx = new Regex(@"^[A-Z]{6}\d{2}[A-Z]\d{2}[A-Z]\d{3}[A-Z]$", RegexOptions.IgnoreCase);

How to match boundary \b with accents

As pointed out by @Callum, Regex101 does not support C#. If you try it in C#, it does work:

    [Test]
    public void TestMatch()
    {
        // Arrange.
        const string example = "123 écumé 456";

        Regex pattern = new Regex(@"\bécumé\b");

        // Act.
        Match match = pattern.Match(example);

        // Assert.
        Assert.That(match.Success, Is.True);
    }

Also to point out that when you say

the following does not find a match: "/\bécumé\b/iu"

The "/iu" in the string is not doing what you might think: in C# you can give regex options using a different parameter, not as part of the pattern string. For example:

Regex pattern = new Regex(@"\bécumé\b", RegexOptions.IgnoreCase);

C# - Regex not matching input string

You should remove / delimiters from all patterns as .NET regexes are defined with string literals, no delimiters are required, and these / chars are part of the patterns that do not match what you expect.

You should replace @"/.[!,@,#,$,%,^,&,*,?,_,~,-,£,(,)]/" with @"[!,@#$%^&*?_~£()-]" to require at least one of these special chars. Note that an unescaped - inside a character class between literals creates a range, thus it is safer to put it at the end (or escape it). NOTE: I kept the comma inside, but since you used it as an OR operator, probably, you should remove it completely. The OR relationship is the default one between atoms in a positive character class.

In all but Regex.Match(password, @"\d+", RegexOptions.ECMAScript) statements, you may safely remove RegexOptions.ECMAScript option that only affects shorthand character class (like \s, \d, etc.).

Use

    if (Regex.Match(password, @"\d+", RegexOptions.ECMAScript).Success)
        score++;
    if (Regex.Match(password, @"[a-z]").Success &&
      Regex.Match(password, @"[A-Z]").Success)
        score++;
    if (Regex.Match(password, @"[!,@#$%^&*?_~£()-]").Success) // check if you need a comma here
        score++;

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