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I want to do a search in real time of objects with Regex in c# [duplicate]

This question already has answers here:
Can I use variables in pattern in Regex (C#)
(2 answers)
Closed 3 years ago.
Is it possible to place a string variable inside a Regex? If so.. how?
I've been playing with regex for 4 hours now and i need just one more thing to finish.
return (new Regex(#"\bA=(\d+[/]\d+)").Match(From).Groups[1].Value.Trim()).ToString();
This line basically gets any fractional number like 42/13 only if it's after "A=" from a string and extracts it.
So here's my question - Is it possible to do something like that:
string variable;
Regex(#"\b"variable"=(\d+[/]\d+)").Match(From).Groups[1].Value.Trim()).ToString();
The idea is to make it so whatever is in variable becomes the regex and for example if in the variable we input D it's now D= now A=.
Thanks in advance.

This is string interpolation. You use the $ operator on your strings to use it. Example
string variable = "hello";
Regex regex = new Regex($#"\b{Regex.Escape(variable)}=(\d+[/]\d+)");

You need to concatenate your strings as usual (+) and prepend # to each string if using backslashes without escaping them. You also don't need to encase / in the character class as [/]. Alternatively, as mentioned by Josh in his answer and Ron Beyer in his comment below your question, you can use interpolation.
#"\b" + variable + #"=(\d+/\d+)"
Additionally, you should use the method Regex.Escape() against your variable to ensure any special characters are escaped (this will prevent your pattern from failing or making incorrect matches) - sanitizing your variable.

Not terminated set of [] in regex (C#) [duplicate]

This question already has answers here:
Regex Match all characters between two strings
(16 answers)
Closed 5 years ago.
I'm trying to parse a text looking for data inside this pattern:
{{([^]+)}}
i.e. any sequence of characters between {{ and }} .
But, when I try to build a Regex object:
Regex _regex = new Regex("{{([^]+)}}", RegexOptions.Compiled);
I got this error:
analysis of "{{([^]+)}}" - Set of [] not terminated....
whatever it means...
Someone has an hint?

The purpose of [^...] is to negate character classes present in the specified list. After the ^ symbol, in order to define a correct regular expression, you should include a set of characters to exclude like, for example [^a]+ (this matches one or more characters that don't include the literal a).
The regex you are attempting to define is probably:
{{\s*([\w]+)\s*}}
Visit this link for trying a working demo.

This is because [^] is not a valid regex, because you need to specify at least one symbol that you wish to exclude.
In order to capture the string up to the closing }} change the expression to this:
{{((?:[^}]|}[^}])*)}}
Demo.

regex expression to accept ENTER key in string [duplicate]

This question already has answers here:
How do I match any character across multiple lines in a regular expression?
(26 answers)
Closed 6 years ago.
Issue
I am having an issue creating a regex to accept any string and the ENTER key, at the moment i have this:
^$|^.+$
I have looked around and people have said to add \n but this does not work.
An example of the string is should allow is as follows:
Hello this is a test string
and i want this to be accepted

Try setting the s flag on the regex engine. This will ensure that the . metacharacter will match newlines.
Here's a link to a working example.
Also, as a sidenote, instead of ^$|^.+$ you can condense the whole expression to ^.*$ to achieve the same results with better performance.

In C#, you need the RegexOptions.Singleline option. See this SO post for more information.
Here is a quick example that really just matches the entire string, so it's not useful.
var regex = new Regex(#"^.*$",
RegexOptions.IgnoreCase | RegexOptions.Singleline);
In your future validation code, you need to replace .* with whatever your validation will be.

C# Regular Expression - find groups in text with a separator [duplicate]

This question already has an answer here:
Learning Regular Expressions [closed]
(1 answer)
Closed 6 years ago.
I have the following text
"a|mother" "b|father"
I want to find via Regex, groups of text that starts with '"' and ends with '"' and separate with '|' without spaces. Meaning the results would be:
"a|mother"
"b|father"
I try to use other posts to solve my question but still with no luck how can I find the |? and how can I find my pattern without spaces?

Something like this:
String source = "\"a|mother\" \"b|father\"";
var result = Regex
.Matches(source, "\"[^\"]*[^ ]\\|[^ ][^\"]*\"")
.OfType<Match>();
Console.Write(String.Join(Environment.NewLine, result));
Output is
"a|mother"
"b|father"

Find tag with contents in HTML using Regex [duplicate]

This question already has an answer here:
Extract Content from Div Tag C# RegEx
(1 answer)
Closed 8 years ago.
I am trying to find tag article and all it's content in HTML string using Regex.
I can successfully match open tag with attrs: <article[^>]*>
I've got issues with matching contents. (.*?) - this technique is not working for me.
Please help.

You cannot use regular expressions to parse HTML in general. However, in constrained scenarios (i.e. when the input follows a rigid structure), you might be able to get away with it. In your case, you can use the following regex, provided that:
The <article> tags are not self-closing
The <article> elements do not contain other <article> descendants
The strings <article and </article> do not appear as literals in your HTML.
Code:
var matches = Regex.Matches(html, #"<article.*?</article>", RegexOptions.Singleline);