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Unable to search for newline character in string

In C#, I'm looking for the index of a string inside a string - specifically the index where the newline (\n) character lives.
Given a string with Windows line breaks (\r\n):
If I look for "\n", it gives me -1. If I look for "\r\n", I get a result. If I look for '\n' as a character, I get a result.
Given a string with Unix line breaks (\n), I get a result.
string s = "hello\r\nworld";
Console.WriteLine(#"\r\n index: " + s.IndexOf("\r\n")); // 5
Console.WriteLine(#"\n index as string: " + s.IndexOf("\n")); // -1
Console.WriteLine(#"\n index as char: " + s.IndexOf('\n')); // 6
s = "hello\nworld";
Console.WriteLine(#"\n index as string: " + s.IndexOf("\n")); // 5
Console.WriteLine(#"\n index as char: " + s.IndexOf('\n')); // 5
I understand that line breaks are two characters, and if I was using StreamReader or File.ReadAllLines or something like that, then it would be handled automatically and I'd lose them.
I thought \n was a valid string by itself, and that \r\n, while special, still represented two separate and distinct characters in a string. But this is telling me otherwise.
I can do IndexOf on the character instead of the string ('\n' instead of "\n"), but I'd really like to know why this is happening so I can plan for it.
EDIT
FYI: Just found that converting the string to a Span gives the correct result. Not sure the overhead involved in that, so I don't know how this compares with the Ordinal solution - I'm guessing the Ordinal is the better one:
Console.WriteLine(#"\n index as string Ordinal: "
+ s.IndexOf("\n", StringComparison.Ordinal)); // 6
Console.WriteLine(#"\n index as Span: "
+ s.AsSpan().IndexOf("\n".AsSpan())); // 6
Console.WriteLine(#"\n index as string with s.AsSpan(): "
+ s.AsSpan().IndexOf("\n")); // 6

There was a change in .Net 5.0 with the globalization libraries for Windows. In previous versions, NLS was used on Windows and ICU on Unix. .Net 5 uses ICU on both to make cross platform development consistent, at the cost of surprising Windows developers (sigh). Due to this change, you must pass StringComparison.Ordinal to find newline in a string.
Note that this can also depend on the version of Windows (double sigh) as Windows 10 May 2019 includes the ICU library and earlier versions that don't will cause .Net 5 to fall back to NLS.
See this article from Microsoft.
This article has more details on the APIs affected.

You may use System.Environment.NewLine in your script, which is a conditional property for the newline character, depending on operating system. Check here.
On Windows: "\r\n".
On unix-platforms: "\n".
using System;
string s = "hello" + Environment.NewLine + "world";

New line character in text file (C#)

I'm exporting text to a file in C# using System.IO.File.AppendAllText, and passing in the text file, and then the text I want to export with \n added to the end. When I view the text document, they are not on different lines, although that pesky return-line character is there between the lines. So the system may think it's two line, but a user sees it as one. How can this be fixed automatically without doing a find-replace every time I generate a file?
System.IO.File.AppendAllText(#"./WarningsLog.txt", line + "\n");

You need to use the Environment.NewLine instead of \n, because newline can be more than that. in windows (if I'm not mistaken), the default is actually \r\n
Although, using \r\n, will help you temporary, using Environment.NewLine is the proper way to go

First off, there are a couple of ways to represent the new line.
The most commonly used are:
The unix way - to write the \n character. \n here represents the newline character.
The windows way - to write the \r\n characters. \r here goes for the carriage return character.
If you are writing something platform-independent, Environment.NewLine will do the job for you and pick the correct character(s).
MSDN states it represents:
A string containing "\r\n" for non-Unix platforms, or a string containing "\n" for Unix platforms.
Also, in some cases you may want to use System.IO.File.AppendAllLines that takes an IEnumerable<string> as the lines collection and appends it to the file. It uses Environment.NewLine inside.

You could try building this with some file specific characters checks , like
new line, tab , etc....
Here is an example code which checks for new line and tabs :
public static string Replace()
{
string rLower = words.ToLower().Replace(Environment.NewLine, "<replaced_newLine>");
rLower = rLower.Replace("\t", "<replaced_Tabulation>");
return rLower;
}
Of course you might have a lot of different combinations , where an item that needs to be changed is followed by " " or "\n" or "\r\n" or "\t"

Confused about C# character special meanings

I'm a newbie in C# programming, and I don't understand how character escaping works. I tried many of them, but only '\t' works like it should.
An example for my code:
textBox1.Text = "asd";
textBox1.Text = textBox1.Text + '\n';
textBox1.Text = textBox1.Text + "asd";
MultiLine is enabled, but my output is simply "asdasd" without breaking the line.
I hope some of you knows what the answer is.

You need "\r\n" for a line break in Windows controls, because that's the normal line break combination for Windows. (Line breaks are the bane of programmers everywhere. Different operating systems have different character sequences that they use as their "typical" line breaks.)
"\r\n" is two characters: \r for carriage return (U+000D) and \n for line feed (U+000A). You don't need to do it in three statements though:
textBox1.Text = "First line\r\nSecond line";
Now, I've deliberately gone with \r\n there instead of Environment.NewLine, on the grounds that if you're working with System.Windows.Forms, those will be Windows-oriented controls. It's unclear to me what an implementation of Windows Forms will do on Mac or Linux, where the normal line break is different. (My guess is that a pragmatic implementation will break on any of \r, \n or \r\n, just like TextReader does, for simplicity.)
Sometimes - such as if you're writing a text file for consumption on the same machine - it's good to use Environment.NewLine.
Sometimes - such as when you're implementing a network protocol such as HTTP which mandates a specific line break format - it's good to be explicit about it.
Sometimes - such as in this case - it's just not clear. However, it's always worth thinking about.
For a complete list of escape sequences in C#, you can either look at the C# language specification (always fun!) or look at my Strings article which contains that information and more.

The most legible way to insert a newline in C# is:
textBox1.Text = "asd";
textBox1.Text = textBox1.Text + Environment.NewLine;
textBox1.Text = textBox1.Text + "asd";
This code snippet would set textBox1 text to "asd", then add a newline to it, then on the second line, it would add "asd" again.
The special characters you are confused about are artifacts from when computers used teletype printers for all of their output. Teletype printers predated digital displays by several years.
\n tells the printer (output) to move the print head down one row (new line).
\r tells the printer (output) to move the print head back to the start of the row (carriage return).
Combined, this resulted in the print head being positioned at the start of the next row, ready for output onto clean paper.
Further information can be sought out on the internet with ease, including places such as Wikipedia's NewLine article

C# - Textbox Newline Problems

I have a textbox, and I'm trying to print to it with the following line of code:
logfiletextbox.Text = logfiletextbox.Text + "\n\n\n\n\n" + o + " copied to " + folderlabel2.Text;
Where folderlabel 2 is obviously a textbox. The first thing I've put in is the same textbox, so that no text is erased. The excessive new lines have proven my problem, because there are no new lines in the textbox (yes, set to multiline). The "o" is of type FileInfo in a FileInfo array.
Why won't these newlines show up in the text box?

Use "\r\n" instead of "\n". Windows text boxes need CRLF as line terminators, not just LF.
Potentially you could use Environment.NewLine instead - but I don't know what Mono TextBoxes do in terms of working with "\n" (which is what Environment.NewLine would be on a Linux box). If it starts putting extra stuff at the end if you use "\r\n" then that will break plenty of existing apps - but if it requires "\r\n" that would break apps which use Environment.NewLine.
Environment.NewLine is meant to be the default new line for the whole platform you're running on - but what if you're using a widget toolkit which does one thing, but text files typically do something else? Frankly it's a bit of a mess. It would be nice if there were a separate TextBox.NewLine property which different implementations could handle appropriately.

I believe TextBoxes want an Environment.NewLine (which should be "\r\n")
Note that it must be the carriage return (\r) followed by the new line (\n). If you reverse the order, it won't work.

A TextBox control expects a Carriage Return before your Line Feeds (0x0D 0x0A). Use "\r\n" or System.Environment.Newline.

in stead of using \n we can use
Environment.NewLine
i hope it will help

This is how i created append and new line for display
txtitems.Text = txtitems.Text + Environment.NewLine + dr[0].ToString() +" "+dr[1].ToString();

Anyone that is using VB.net, be on the lookout for vbCr
Here is an example:
return "My name is" & vbCr & "John" & vbCr & "Doe"

C# Reading a file and writing out replacing string

What I have is a C# windows app that reads a bunch of SQL tables and creates a bunch of queries based on the results. What I'm having a small issue with is the final "," on my query
This is what I have
ColumnX,
from
I need to read the entire file, write out exactly what is in the file and just replace the last , before the from with nothing.
I tried .replace(#",\n\nfrom),(#"\n\nfrom) but it's not finding it. Any help is appreciated.
Example:
ColumnX,
from
Result:
ColumnX
from

The line break is most likely the two character combination CR + LF:
.replace(",\r\n\r\nfrom","\r\n\r\nfrom")
If you want the line break for the current system, you can use the Environment.NewLine constant:
.replace(","+Environment.NewLine+Environment.NewLine+"from",Environment.NewLine+Environment.NewLine+"from")
Note that the # in front of a string means that it doesn't use backslash escape sequences, but on the other hand it can contain line breaks, so you could write it in this somewhat confusing way:
str = str.replace(#",
from", #"
from");

There are two solutions that you can try:
Remove the # symbol, as that means it's going to look for the literal characters of \n rather than a newline.
Try .replace("," + Environment.NewLine + Environment.NewLine + from, Environment.NewLine + Environment.NewLine + "from)

Instead of replacing or removing the comma when you read the file, it would probably be preferable to remove it before the file is written. That way you only have to bother with the logic once. As you are building your column list, just remove the last comma after the list is created. Hopefully you are in a position where you have control over that process.

If you can assume you always want to remove the last occurrence of the comma you can use the string function LastIndexOf to find the index for the last comma and use Remove from there.
myString = myString.Remove(myString.LastIndexOf(","), 1);

What about using Regex? Does that handle different forms of linefeed better?
var result = Regex.Replace(input, #",(\n*)from", "$1from");