Develop Reference

How does Visual Studio syntax-highlight strings in the Regex constructor?

Hi fellow programmers and nerds!
When creating regular expressions Visual Studio, the IDE will highlight the string if it's preceded by a verbatim identifier (for example, #"Some string). This looks something like this:
(Notice the way the string is highlighted). Most of you will have seen this by now, I'm sure.
My problem: I am using a package acquired from NuGet which deals with regular expressions, and they have a function which takes in a regular expression string, however their function doesn't have the syntax highlighting.
As you can see, this just makes reading the Regex string just a pain. I mean, it's not all-too-important, but it would make a difference if we can just have that visually-helpful highlighting to reduce the time and effort one's brain uses trying to decipher the expression, especially in a case like mine where there will be quite a quantity of these expressions.
The question
So what I'm wanting to know is, is there a way to make a function highlight the string this way*, or is it just something that's hardwired into the IDE for the specific case of the Regex c-tor? Is there some sort of annotation which can be tacked onto the function to achieve this with minimal effort, or would it be necessary to use some sort of extension?
*I have wrapped the call to AddStyle() into one of my own functions anyway, and the string will be passed as a parameter, so if any modifications need to be made to achieve the syntax-highlight, they can be made to my function. Therefore the fact that the AddStyle() function is from an external library should be irrelevant.
If it's a lot of work then it's not worth my time, somebody else is welcome to develop an extension to solve this, but if there is a way...
Important distinction
Please bear in mind I am talking about Visual Studio, NOT Visual Studio Code.
Also, if there is a way to pull the original expression string from the Regex, I might do it that way, since performance isn't a huge concern here as this is a once-on-startup thing, however I would prefer not to do it that way. I don't actually need the Regex object.

According to https://devblogs.microsoft.com/dotnet/visual-studio-2019-net-productivity/#regex-language-support and https://www.meziantou.net/visual-studio-tips-and-tricks-regex-editing.htm you can mark the string with a special comment to get syntax highlighting:
// language=regex
var str = #"[A-Z]\d+;
or
MyMethod(/* language=regex */ #"[A-Z]\d+);
(the comment may contain more than just this language=regex part)
The first linked blog talks about a preview, but this feature is also present in the final product.

.NET 7 introduces the new [StringSyntax(...)] attribute, which is used in .NET 7 on more than 350 string, string[], and ReadOnlySpan<char> parameters, properties, and fields to highlight to an interested tool what kind of syntax is expected to be passed or set.
https://devblogs.microsoft.com/dotnet/regular-expression-improvements-in-dotnet-7/?WT_mc_id=dotnet-35129-website&hmsr=joyk.com&utm_source=joyk.com&utm_medium=referral
So for a method argument you should just use:
void MyMethod([StringSyntax(StringSyntaxAttribute.Regex)] string regex);
Here is a video demonstrating the feature: https://youtu.be/Y2YOaqSAJAQ

C# , How to write RegEx.Replace to replace value for an xml element?

Have a xml string, goal is to replace an xml element value to a fixed string, i.e. for blah blah blah replace it to fixed value, I am thinking to use RegEx.Replace instead of loading the string to a DOM model and replace.
Could anyone please help on how to write this regular expression? essentially the goal is to match everything inside element tag 'abc'
Thanks a lot!

This article tells you what you need to know: XML is not Regular
Ignoring the most obvious solution to their problem (which would be to use a pre-existing XML parser), they think they should use regular expressions (regex for short). Now they have two problems.
Use regular expressions only on regular languages.
That said, there are many sites that purport to offer guidance on writing regular expressions for XML. They are all wrong. But they exist, and you can use them at your own risk.

For what it's worth, don't.
Process the XML normally, with a XmlDocument, Xml.Linq or XmlReader/Writer, it's what they are for, cover all kinds of edge cases we couldn't even imagine, and above all, are proven to work.
Don't use a regex for this, please . . . just don't.
My two cents.
let the downvoting begin

Regular expressions are meant to be used on regular languages. XML is a non-regular language. As such, regular expressions cannot be used to properly parse anything written in it. You will need to use a real XML parser, which can be found in the numerous libraries available in C#, to do it.

Regular expressions are not suitable for processing markup. Among other flaws, they won't work if elements can be nested:
<abc> ... <abc> ... </abc> ... </abc>
They are also unable to distinguish a comment from a non-comment.
You need a real XML parser.

How does wikimedia transform its model syntax?

I would like to know how does Wikimedia transform its model syntax ({{model|options}}) into html code.
I have a regex for a simple model ({{.*?}}) but it fails for a nested model (ex: {{model|options containing a {{submodel|options}}...}})

Remember,
Some people, when confronted with a problem, think "I know, I'll use
regular expressions." Now they have two problems. - Jamie Zawinski
That said, you can read: Forum tags. What is the best way to implement them? I made an example of nested tags, both with "pure" Regex and with a "more stable" C# parser that uses a little of Regexes but keeps the stack out of the Regex hands.
You can do it with balancing groups. They aren't part of "base" Regex (and some persons don't consider them to be true regexes),
But I wouldn't program something as big as Wiki with something like a regex. The problem of regexes is that it's quite difficult to program them so that they don't backtrack (there is an option to do it, but it's difficult to build a regex that doesn't need backtracking or that need only limited amout of backtracking), and when they begin to backtrack it's the end: they could stall for minutes searching for the right combination of captures.

Regular expression in C# , is this possible?

I never use regular expression before and plan to use it to solve my problem but not quite sure whether it can help me.
I have a situation where I need store a rule or formula to build string values like following examples in a database field then retrieve this rule and build the string value.
FacilityCode + Left(ModelNO,2)
Right(PO,3) + Left(Serial,2)
Is this achievable using .net regular expression? Any good tutorial or simple examples of this problem.

Regexp : http://msdn.microsoft.com/en-us/library/2k3te2cs(VS.80).aspx
http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex.aspx
But it doesn't seems fitting :)

It might be better to code some random string generator. Regex is for searching data not creating data.
The thing to remember about regex is that it is like an aircraft carrier; it does one thing very very well, it does not do other jobs very well at all.
An aircraft carrier moves planes very well on the ocean; it does not make a cheese sandwich well AT ALL!!
That is to say, if you use regex when you shouldn't you will almost certainly use far more processing power than if you used another tool for that job. Html parsing comes to mind.

Regex is provided as part of System.Text.RegularExpressions, but you can't rely exclusively on it. It'll let you search existing strings, but you'll need to implement your own logic for building new strings based on what you find in the existing data.
Also, keep in mind that System.Text.RegularExpressions works differently from regexp in Perl and other implementations. For example, it doesn't recognize POSIX character class definitions.
Since you're new to regex, you might want to check out the "Regular Expressions User Guide" on zytrax.com. It's not as comprehensive as an O'Reilly manual, but it'll do as a start.

ANTLR or Regex?

I'm writing a CMS in ASP.NET/C#, and I need to process things like that, every page request:
<html>
<head>
<title>[Title]</title>
</head>
<body>
<form action="[Action]" method="get">
[TextBox Name="Email", Background=Red]
[Button Type="Submit"]
</form>
</body>
</html>
and replace the [...] of course.
My question is how should I implement it, with ANTLR or with Regex? What will be faster? Note, that if I'm implementing it with ANTLR I think that I will need to implement XML, in addon to the [..].
I will need to implement parameters, etc.
EDIT: Please note that my regex can even look like something like that:
public override string ToString()
{
return Regex.Replace(Input, #"\[
\s*(?<name>\w+)\s*
(?<parameter>
[\s,]*
(?<paramName>\w+)
\s*
=
\s*
(
(?<paramValue>\w+)
|
(""(?<paramValue>[^""]*)"")
)
)*
\]", (match) =>
{
...
}, RegexOptions.IgnorePatternWhitespace);
}

Whether the correct tool is RegEx or ANTLR or even something else entirely should be heavily dependent on your requirements. The best answer to a "what tool to use" question shouldn't be primarily based on performance, but on the right tool for the job.
RegEx is a text search tool. If all you need to do is pull strings out of strings then it's often the hammer of choice. You'll likely want a tool to help you build your RegEx. I'd recommend Expresso, but there are lots of options out there.
ANTLR is a compiler generator. If you need error messages and parse actions or any of the complicated things that come with a compiler then it's a good option.
What it looks like you're doing is XML search/replace, have you considered XPath? That would be my suggestion.
Choosing the right tool for the job is definitely important, something that should be researched and thought out before development begins. In all cases, it's important to fully understand the program requirements before making any decisions. Do you have a specification for the project? If not, spending the time to come up with one will save you all the time that a poor tool choice can cost you.
Hope that helps!

About the performance of ANTLR vs. RegEx depends on the implementation of RegEx in C#. I know, from experience, that ANTLR is fast enough.
In ANTLR you can ignore certain content, like the XML. You can also seek for the [ and ] and go further with processing.
Both RegEx and ANTLR are supporting your kind of parameters (the "etc." I'm not sure about).
In terms of development speed: RegEx is slightly faster for such a case like this. You can use an online tool to develop the RegEx and see the capture-groups while you edit the RegEx. (Google # regex gskinner)
Then ANTLR has perfect support for "error-messages": they show line/column numbers and what was wrong. RegEx doesn't have this support.
A general approach for RegEx would be: create a "global scan" RegEx which will find correct [...] groups in your content. Then let the "..." be captuerd by a group, and then apply another RegEx for this smaller content (which splits content based on the equal-sign and commas). This way you have the best runtime performance and it's easy to develop.

If the language you are parsing is regular then regular expressions are certainly an option. If it is not then ANTLR may be your only choice. If I understand these matters correctly XML is not regular.