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What is the proper RegEx to grab all blocks of SAS code that start with 'proc sql;' and end with 'quit;'?

I have this:
var blockRegEx = new Regex("(proc sql;)(.*?)(quit;)", RegexOptions.IgnoreCase |
RegexOptions.Multiline);
but it only works if the string is on a single line.
For example:
proc sql;
create table xtr as
select
midsu_client_id,
prodt_cd,
confmt_ind,
maj_diag_categ,
mbr_num,
pay_amt format=comma16.2
from cr_data.rptng
where &acctnum
and gl_postg between "&date_1" and "&date_2"
;
quit;

RegexOptions.MultiLine changes the behavior of the '^' and '$' characters:
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.
Multiline is useful if you're passing multiple lines at once into your regex search and you want to treat them as multiple lines (i.e. they all start with '^' and end with '$').
I think you want to try using RegexOptions.SingleLine instead:
Specifies single-line mode. Changes the meaning of the dot (.) so it
matches every character (instead of every character except \n).
SingleLine is useful if you're passing multiple lines at once into your regex search and you want to treat them as thought they were actually all a single line.

C# Regex find string between two strings with newLine

Here is my regex: Regex r = new Regex("start(.*?)end", RegexOptions.Multiline);
That means I want to get the stuff between "start" and "end". But the problem is that between start and end is a new line or \n and the regex doesn't return anything.
So how do I make regex find \n?

The name of the Multiline option is misleading, as is the one of the correct option - Singleline:
Regex r = new Regex("start(.*?)end", RegexOptions.Singleline);
From MSDN, RegexOptions Enumeration:
Singleline - Specifies single-line mode. Changes the meaning of the dot (.) so it matches every character (instead of every character except \n).

Include the RegexOptions.SingleLine which means that . matches everything, including \n
Regex r = new Regex("start(.*?)end", RegexOptions.Multiline | RegexOptions.SingleLine);
See http://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regexoptions.aspx for more details.

Use Singleline instead of Multiline:
Regex r = new Regex("start(.*?)end", RegexOptions.Singleline);
BTW, RegexBuddy is your invaluable friend (No, I'm not connected whatsoever to the author, except for being a happy user).

Checking lines of a file against a regex

I am using the Regex.Match method to find a credit card number within a file (for PCI compliance)
I interate through the lines (strLine) of a file and check each one against a regex (m_strRegEx):
Regex.Match(strLine, m_strRegEx)
string strLine = "4111111111111111"
This works fine, but if the line contains other characters, for example strLine might =:
string strLine = "fhj*4111111111111111op)"
The regex does not then pick the cc number up, how would it be possible to overcome this issue?
The regex I am using is:
^4[0-9]{12}(?:[0-9]{3})?$

This is because your regex is anchored to the start and end of the string with ^ and $. This means that the entire string has to match your regex and not just a substring.
Remove the ^ and $ from the regex to perform a substring match:
4[0-9]{12}(?:[0-9]{3})?
Quick test:
PS> 'fhj*4111111111111111op)' -match '4[0-9]{12}(?:[0-9]{3})?'; $Matches
True
Name Value
---- -----
0 4111111111111111

As your regex starts with ^ and ends with $ this means that the match must be from the start to the end of the line. Just remove these characters from your regex pattern and it should work as you require.

You should remove the anchors:
4[0-9]{12}(?:[0-9]{3})?

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.)

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