verify that string matches a regex pattern [duplicate] - c#

This question already has an answer here:
Reference - What does this regex mean?
(1 answer)
Closed 3 years ago.
Is there a way to verify with Regex that a string matches a patter like so:
1.001
1.002
15.001
Where the pattern is:
any number followed by
dot character
followed by three (3) numbers
Given that patters things like this would fail:
A.001
1.0001
1,001
...
Any help is appreciated.

This regex should work:
^\d+\.\d{3}$

Related

How to get all possible Regex Matches [duplicate]

This question already has answers here:
C# Code to generate strings that match a regex [closed]
(4 answers)
Closed 3 years ago.
Based off a regex string I would like to get a list of all the possible strings that would match the regex.
Example:
Given a regex string like...
^(en/|)resources/case(-| )studies/
I want to get a list of all the possible strings that would match the regex expression. Like...
^en/resources/case-studies/
or
^/resources/case-studies/
or
^en/resources/case studies/
or
^/resources/case studies/
Thank you
Note that in regex ^ denotes the beginning of the line. You must escape it
Try
\^(en)?/resources/case(-|\s)studies/
explanation:
\^ is ^ escaped.
(en)? is optionally en, where ? means zero or one times.
/resources/case the text as is.
(-|\s) minus sign or white space.
studies/ the text as is.
See: https://dotnetfiddle.net/PO4wKV

Regex expression to verify that a string only contains letters, numbers, underscores and dashes [duplicate]

This question already has answers here:
Reference - What does this regex mean?
(1 answer)
What do ^ and $ mean in a regular expression?
(2 answers)
Closed 3 years ago.
I've already read this here and I still have got some questions. I will be very grateful if you can help me to solve them. I'm trying to compose a RegEx to verify that a string contains only letters, numbers, underscores and hyphens. Firstly, when I tried to do it (without Google-search) I did this #"[A-Za-z0-9_-]". After I made some research I found that it should be #"^[a-zA-Z0-9_-]$" where:
^ asserts position at start of a line
$ asserts position at the end of a line
My question is why we should insert these symbols? And my other question is why the string "jeffbutt" (with yellow in the screenshot) doesn't match?

Use RegEx to find 100$ in text c# [duplicate]

This question already has answers here:
C# Regex Match whole word, with special characters
(2 answers)
Regex whitespace word boundary
(3 answers)
Closed 4 years ago.
I am trying to search 100$ through the RegEx. But unable to find its pattern is as above.
\b100\$\b
However, if the text contains 100$1 then it displays properly.
But I want to do exact search.
Word boundaries only work with word characters, not $. Try using this regex:
\b100\$(?=\s|\$)
This will match 100$, where what follows the $ is either whitespace or the end of the line.
Demo

how to match "test\w*" but not "tester" with a single regex expression [duplicate]

This question already has answers here:
Regular expression to match a line that doesn't contain a word
(34 answers)
Closed 8 years ago.
Say I have the following string:
test tester tested testing
I wish to match every word that begins with test, but not the word tester. The pattern test\w* does most of the job, but I have no idea how to add that tester should not be matched. A working pattern should give 3 matches on the string.
Does this work for your purposes?
test(?!er).*

I still don't understand regular expression [duplicate]

This question already has an answer here:
Reference - What does this regex mean?
(1 answer)
Closed 8 years ago.
I have this piece of code but have no idea what it is supposed to be matching. I have looked at many different sites to try and learn the keywords, but I just don't understand regex.
string key = #"^(.*)\s*=\s*(.*)\s*$";
Match value = Regex.Match(line, key);
This looks for the start of a line (^), finds any number of characters ((.*)), followed by some whitespace (\s*) an equal sign (=) some more whitespace (\s*) and any number of characters ((.*)) and the end of line ($)
Some valid example lines:
a=a
abc = xyz
value=5
etc

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