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How to match string format in Regex c#

I am passing a correct string formate but its not return true.
string dimensionsString= "13.5 inches high x 11.42 inches wide x 16.26 inches deep";
// or 10.1 x 12.5 x 30.9 inches
// or 10.1 x 12.5 x 30.9 inches ; 3.2 pounds
Regex rgxFormat = new Regex(#"^([0-9\.]+) ([a-z]+) x ([0-9\.]+) ([a-z]+) x ([0-9\.]+) ([a-z]+)( ; ([0-9\.]+) ([a-z]+))?$");
if (rgxFormat.IsMatch(dimensionsString))
{
//match
}
I can't understand whats wrong with code ?

Your pattern only accounts for single words after the numbers. Allow any number of symbols there (with .* or .*?) to fix the pattern:
^([0-9.]+) (.*?) x ([0-9\.]+) (.*?) x ([0-9.]+) (.*?)( ; ([0-9.]+) (.*))?$
See the regex demo.
Note that the last .* is used with a greedy quantifier since it is the last unknown bit in the string (to match all the rest of the string). The .*? are non-greedy versions that match as few occurrences of any char but a newline as possible.
Replace regular spaces with \s to match any kind of whitespace if necessary.

Replace floating numbers in math equation with letter variables

I want to replace all the floating numbers from a mathematical expression with letters using regular expressions. This is what I've tried:
Regex rx = new Regex("[-]?([0-9]*[.])?[0-9]+");
string expression = "((-30+5.2)*(2+7))-((-3.1*2.5)-9.12)";
char letter = 'a';
while (rx.IsMatch(expression))
{
expression = rx.Replace(expression , letter.ToString(), 1);
letter++;
}
The problem is that if I have for example (5-2)+3 it will replace it to: (ab)+c
So it gets the -2 as a number but I don't want that.
I am not experienced with Regex but I think I need something like this:
Check for '-', if there is a one, check if there is a number or right parenthesis before it. If there is NOT then save the '-'.
After that check for digits + dot + digits
My above Regex also works with values like: .2 .3 .4 but I don't need that, it should be explicit: 0.2 0.3 0.4

Following the suggested logic, you may consider
(?:(?<![)0-9])-)?[0-9]+(?:\.[0-9]+)?
See the regex demo.
Regex details
(?:(?<![)0-9])-)? - an optional non-capturing group matching 1 or 0 occurrences of
(?<![)0-9]) - a place in string that is not immediately preceded with a ) or digit
- - a minus
[0-9]+ - 1+ digits
(?:\.[0-9]+)? - an optional non-capturing group matching 1 or 0 occurrences of a . followed with 1+ digits.
In code, it is better to use a match evaluator (see the C# demo online):
Regex rx = new Regex(#"(?:(?<![)0-9])-)?[0-9]+(?:\.[0-9]+)?");
string expression = "((-30+5.2)*(2+7))-((-3.1*2.5)-9.12)";
char letter = (char)96; // char before a in ASCII table
string result = rx.Replace(expression, m =>
{
letter++; // char is incremented
return letter.ToString();
}
);
Console.WriteLine(result); // => ((a+b)*(c+d))-((e*f)-g)

Regex - Trying to write match validation for Swedish Social Number

So I want the formats xxxxxx-xxxx AND xxxxxxxx-xxxx to be possible. I've managed to fix the first section before the dash, but the last four digits are troublesome. It does require to match at least 4 characters, but I also want the regex to return false if there's more than 4 characters. How do I do it?
This is how it looks so far:
var regex = new Regex(#"^\d{6,8}[-|(\s)]{0,1}\d{4}");
And this is the results:
var regex = new Regex(#"^\d{6,8}[-|(\s)]{0,1}\d{4}");
Match m = regex.Match("840204-2344");
Console.WriteLine(m.Success); // Outputs True
Match m = regex.Match("19840204-2344");
Console.WriteLine(m.Success); // Outputs True
Match m = regex.Match("19840204-23");
Console.WriteLine(m.Success); // Outputs false
Match m = regex.Match("19840204-2323423423");
Console.WriteLine(m.Success); // Outputs true, and this is what I don't want

The \d{6,8} pattern matches 6, 7 or 8 digits, so that will already invalidate your regex pattern. Besdies, [-|(\s)]{0,1} matches 1 or 0 -, (, ), | or whitespace chars, and will also match strings like 19840204|2323, 19840204(2323 and 19840204)2323.
You may use
^\d{6}(?:\d{2})?[-\s]?\d{4}$
See the regex demo.
Details
^ - start of string
\d{6} - 6 digits
(?:\d{2})? - optional 2 digits
[-\s]? - 1 or 0 - or whitespaces
\d{4} - 4 digits
$ - end of string.
To make \d only match ASCII digits, pass RegexOptions.ECMAScriptoption. Example:
var res = Regex.IsMatch(s, #"^\d{6}(?:\d{2})?[-\s]?\d{4}$", RegexOptions.ECMAScript);

You are forgetting the $ at the end:
var regex = new Regex(#"^(\d{6}|\d{8})-\d{4}$");
If you want to match the social security number anywhere in a string, you van also use \b to test for boundaries:
var regex = new Regex(#"\b(\d{6}|\d{8})-\d{4}\b");
Edit: I corrected the RegEx to fix the problems mentioned in the comments. The commentors are right, of course. In my earlier post I just wanted to explain why the RegEx matched the longer string.

How to write a regular expression that captures tags in a comma-separated list?

Here is my input:
#
tag1, tag with space, !##%^, 🦄
I would like to match it with a regex and yield the following elements easily:
tag1
tag with space
!##%^
🦄
I know I could do it this way:
var match = Regex.Match(input, #"^#[\n](?<tags>[\S ]+)$");
// if match is a success
var tags = match.Groups["tags"].Value.Split(',').Select(x => x.Trim());
But that's cheating, as it involves messing around with C#. There must be a neat way to do this with a regex. Just must be... right? ;D
The question is: how to write a regular expression that would allow me to iterate through captures and extract tags, without the need of splitting and trimming?

This works (?ms)^\#\s+(?:\s*((?:(?!,|^\#\s+).)*?)\s*(?:,|$))+
It uses C#'s Capture Collection to find a variable amount of field data
in a single record.
You could extend the regex further to get all records at once.
Where each record contains its own variable amount of field data.
The regex has built-in trimming as well.
Expanded:
(?ms) # Inline modifiers: multi-line, dot-all
^ \# \s+ # Beginning of record
(?: # Quantified group, 1 or more times, get all fields of record at once
\s* # Trim leading wsp
( # (1 start), # Capture collector for variable fields
(?: # One char at a time, but not comma or begin of record
(?!
,
| ^ \# \s+
)
.
)*?
) # (1 end)
\s*
(?: , | $ ) # End of this field, comma or EOL
)+
C# code:
string sOL = #"
#
tag1, tag with space, !##%^, 🦄";
Regex RxOL = new Regex(#"(?ms)^\#\s+(?:\s*((?:(?!,|^\#\s+).)*?)\s*(?:,|$))+");
Match _mOL = RxOL.Match(sOL);
while (_mOL.Success)
{
CaptureCollection ccOL1 = _mOL.Groups[1].Captures;
Console.WriteLine("-------------------------");
for (int i = 0; i < ccOL1.Count; i++)
Console.WriteLine(" '{0}'", ccOL1[i].Value );
_mOL = _mOL.NextMatch();
}
Output:
-------------------------
'tag1'
'tag with space'
'!##%^'
'??'
''
Press any key to continue . . .

Nothing wrong with cheating ;]
string input = #"#
tag1, tag with space, !##%^, 🦄";
string[] tags = Array.ConvertAll(input.Split('\n').Last().Split(','), s => s.Trim());

You can pretty much make it without regex. Just split it like this:
var result = input.Split(new []{'\n','\r'}, StringSplitOptions.RemoveEmptyEntries).Skip(1).SelectMany(x=> x.Split(new []{','},StringSplitOptions.RemoveEmptyEntries).Select(y=> y.Trim()));

How to match string that contains ^ in regular expression?

I tried to make a regular expression using online tool but not succeeded. Here is the string i need to match:-
27R4FF^27R4FF Text until end
always starts with alphanumeric (case-insensitive)
then always caret sign ^ (no space before & after)
then alphanumeric string
then always one white space
then string until end.
Here is the regular expression that is not working for me:-
((?:[a-z][a-z]*[0-9]+[a-z0-9]*))(\^)((?:[a-z][a-z]*[0-9]+[a-z0-9]*)).*?((?:[a-z][a-z]+))
c# code:-
string txt = "784SFS^784SFS Value is here";
var regs = #"((?:[a-z][a-z]*[0-9]+[a-z0-9]*))(\^)((?:[a-z][a-z]*[0-9]+[a-z0-9]*)).*?((?:[a-z][a-z]+))";
Regex r = new Regex(regs, RegexOptions.IgnoreCase | RegexOptions.Singleline);
Match m = r.Match(txt);
Console.Write(m.Success ? "matched" : "didn't match");
Console.ReadLine();
Help appreciated. Thanks

Verbatim ^[^\W_]+\^[^\W_]+[ ].*$
^ # BOS
[^\W_]+ # Alphanum
\^ # Caret
[^\W_]+ # Alphanum
[ ] # Space
.* # Anything
$ # EOS
Output
** Grp 0 - ( pos 0 , len 28 )
27R4FF^27R4FF Text until end

I didn't get if string 'until the end' should be matched.
This works for
27R4FF^27R4FF Text
^\w+\^\w+\s\w+$
if you have some spaces at the end, try with
^\w+\^\w+\s[\w\s]+$

Try this: https://regex101.com/r/hD0hV0/2
^[\da-z]+\^[\da-z]+\s.*$
...or commented (assumes RegexOptions.IgnorePatternWhitespace if you're using the format in code):
^ # always starts...
[\da-z]+ # ...with alphanumeric (case-insensitive)
\^ # then always caret sign ^ (no space before & after)
[\da-z]+ # then alphanumeric string
\s # then always one white space
.* # then string...
$ # ...until end.
The other answers don't actually match what you describe (at the time of this writing) because \w matches underscore and you didn't mention any limitations on "the string at the end".