Regex That Matches a Newline (\N) in C#

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

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).

Why does regex detect newline as a valid newline but not \n?

from what Tim Biegeleisen said, "on windows the line separator is not just \n, it's \r\n", with this I changed pattern 2 to \d{1,}\r\n\w and everything turned out fine.

Replace a new line char with regex in C#

In Windows, line breaks usually look like \r\n (caret return + line feed).
So, you can match linebreaks that are preceded and followed by an alphanumeric with

string output = Regex.Replace(pathFOSE, @"(?<=\w)\r\n(?=\w)", " ");

Mind that \w matches Unicode letters and an underscore, too. If you do not need that behavior (and only need to match English letters) use

string output = Regex.Replace(pathFOSE, @"(?i)(?<=[a-z0-9])\r\n(?=[a-z0-9])", " ");

If you have a mixture of line breaks from various OSes or programs, you may use

string output = Regex.Replace(pathFOSE, @"(?i)(?<=[a-z0-9])(?:\r\n|\n|\r)(?=[a-z0-9])", " ");

And in case there are multiple line breaks, add a + quantifier (?:\r\n|\n|\r)+.

To perform search and replace on the file contents, you need to read the file in.

You can do it with

var pathFOSE = @"D:\Public\temp\FOSEtest.txt";
var contents = File.ReadAllText(pathFOSE);
var output = Regex.Replace(contents, @"(?i)(?<=[a-z0-9])(?:\r\n|\n|\r)(?=[a-z0-9])", " ");

var pathNewFOSE = @"D:\Public\temp\NewFOSE.txt";
if (!System.IO.File.Exists(pathNewFOSE))
{
    File.WriteAllText(pathNewFOSE, output);
}

How do I match any character across multiple lines in a regular expression?

It depends on the language, but there should be a modifier that you can add to the regex pattern. In PHP it is:

/(.*)<FooBar>/s

The s at the end causes the dot to match all characters including newlines.

Regex replace multiple new lines

The point is that your regex matches sequences of \r\n (2 or more) and then 2 or more sequences of \r\r. You need

[\r\n]+

Or [\r\n]{2,} if you need to only match 2 or more occurrences of \r or \n.

If you need to exactly match 2 or more common line break types (\r\n in Windows, \n in Unix/Linux and \r on Mac OS), use

(?:\r?\n|\r){2,}

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