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Remove non-alphanumeric characters from start and end of string only

I am trying to clean up some data using a helper exe (C#).
I iterate through each string and I want to remove invalid characters from the start and end of the string i.e. remove the dollar symbols from $$$helloworld$$$.
This works fine using this regular expression: \W.
However, strings which contain invalid character in the middle should be left alone i.e. hello$$$$world is fine and my regular expression should not match this particular string.
So in essence, I am trying to figure out the syntax to match invalid characters at the start and the end of of a string, but leave the strings which contain invalid characters in their body.
Thanks for your help!

This does it!
(^[\W_]*)|([\W_]*$)
This regex says match zero or more non word characters at the start(^) or(|) at the end($)

The following should work:
^\W+|\W+$
^ and $ are anchors to the beginning and end of the string respectively. The | in the middle is an OR, so this regex means "either match one or more non-word characters at the start of the string, or match one or more non-word characters at the end of the string".

Use ^ to match the start of string, and $ to match the end of string. C# Regex Cheat Sheet

Try this one,
(^[^\w]*)|([^\w]*$)

Use ^ to match 'beginning of line' and $ to match 'end of line', i.e. you code should match and remove ^\W* and \W*$

.net regex match line

Why does ^.*$ does not match a line in:
This is some sample text
this is another line
this is the third line
how can I create a regular expression that will match an entire line so that when finding the next match it will return me the next line.
In other words I will like to have a regex so that the first match = This is some sample text , next match = this is another line etc...

^ and $ match on the entire input sequence. You need to use the Multiline Regex option to match individual lines within the text.
Regex rgMatchLines = new Regex ( #"^.*$", RegexOptions.Multiline);
See here for an explanation of the regex options. Here's what it says about the Multiline option:
Multiline mode. Changes the meaning of ^ and $ so they match at the
beginning and end, respectively, of any line, and not just the
beginning and end of the entire string.

use regex options
Regex regex = new Regex("^.*$", RegexOptions.Multiline);

You have to enable RegexOptions.Multiline to make ^ and $ matches the start and end of line. Otherwise, ^ and $ will match the start and end of the whole input string.

Regex to match full lines of text excluding crlf

How would a regex pattern to match each line of a given text be?
I'm trying ^(.+)$ but it includes crlf...

Just use RegexOptions.Multiline.
Multiline mode. Changes the meaning of
^ and $ so they match at the beginning
and end, respectively, of any line,
and not just the beginning and end of
the entire string.
Example:
var lineMatches = Regex.Matches("Multi\r\nlines", "^(.+)$", RegexOptions.Multiline);

I'm not sure what you mean by "match each line of a given text" means, but you can use a character class to exclude the CR and LF characters:
[^\r\n]+

The wording of your question seems a little unclear, but it sounds like you want RegexOptions.Multiline (in the System.Text.RegularExpressions namespace). It's an option you have to set on your RegEx object. That should make ^ and $ match the beginning and end of a line rather than the entire string.
For example:
Regex re = new Regex("^(.+)$", RegexOptions.Compiled | RegexOptions.Multiline);

Have you tried:
^(.+)\r?\n$
That way the match group includes everything except the CRLF, and requires that a new line be present (Unix default), but accepts the carriage return in front (Windows default).

I assume you're using the Multiline option? In that case you'll want to match the newline explicitly with "\n". (substitute "\r\n" as appropriate.)

How to check if a Regex expression matches an entire string in c#?

I am new to regex expressions so sorry if this is a really noob question.
I have a regex expression... What I want to do is check if a string matches the regex expression in its entirety without the regex expression matching any subsets of the string.
For example...
If my regex expression is looking for a match of \sA\s*, it should return a match if the string it is comparing it to is " A " but if it compares to the string " A B" it should not return a match.
Any help would be appreciated? I code in C#.

You would normally use the start end end anchors ^ and $ respecitvely:
^\s*A*\s*$
Keep in mind that, if you regex engine supports multi-line, this may also capture strings that span multiple lines as long as one of those lines matches the regex(since ^ then anchors after any newline or string-start and $ before any newline or string end). If you're only running the regex against a single line, that won't be a problem.
If you want to ensure that a multi-line input is only a single line consisting of your pattern, you can use \A and \Z if supported - these mean start and end of string regardless of newlines.

If you cannot or don't want to change the regular expression, then you can also use:
var match = regex.Match(pattern);
if (match.Success && match.Length == pattern.Length)
{
// TODO: Entire string was matched, and not a sub string
}

Regex that matches a newline (\n) in C#

OK, this one is driving me nuts....
I have a string that is formed thus:
var newContent = string.Format("({0})\n{1}", stripped_content, reply)
newContent will display like:
(old text)
new text
I need a regular expression that strips away the text between parentheses with the parenthesis included AND the newline character.
The best I can come up with is:
const string regex = #"^(\(.*\)\s)?(?<capture>.*)";
var match= Regex.Match(original_content, regex);
var stripped_content = match.Groups["capture"].Value;
This works, but I want specifically to match the newline (\n), not any whitespace (\s)
Replacing \s with \n \\n or \\\n does NOT work.
Please help me hold on to my sanity!
EDIT: an example:
public string Reply(string old,string neww)
{
const string regex = #"^(\(.*\)\s)?(?<capture>.*)";
var match= Regex.Match(old, regex);
var stripped_content = match.Groups["capture"].Value;
var result= string.Format("({0})\n{1}", stripped_content, neww);
return result;
}
Reply("(messageOne)\nmessageTwo","messageThree") returns :
(messageTwo)
messageThree

If you specify RegexOptions.Multiline then you can use ^ and $ to match the start and end of a line, respectively.
If you don't wish to use this option, remember that a new line may be any one of the following: \n, \r, \r\n, so instead of looking only for \n, you should perhaps use something like: [\n\r]+, or more exactly: (\n|\r|\r\n).

Actually it works but with opposite option i.e.
RegexOptions.Singleline

You are probably going to have a \r before your \n. Try replacing the \s with (\r\n).

Think I may be a bit late to the party, but still hope this helps.
I needed to get multiple tokens between two hash signs.
Example i/p:
## token1 ##
## token2 ##
## token3_a
token3_b
token3_c ##
This seemed to work in my case:
var matches = Regex.Matches (mytext, "##(.*?)##", RegexOptions.Singleline);
Of course, you may want to replace the double hash signs at both ends with your own chars.
HTH.

Counter-intuitive as it is, you can use both Multiline and Singleline option.
Regex.Match(input, #"(.+)^(.*)", RegexOptions.Multiline | RegexOptions.Singleline)
First capturing group will contain first line (including \r and \n) and second group will have second line.
Why:
First of all RegexOptions enum is flag so it can be combined with bitwise operators, then
Multiline:
^ and $ match the beginning and end of each line (instead of the beginning and end of the input string).
Singleline:
The period (.) matches every character (instead of every character except \n)
see docs