Why is Environment.NewLine = "\r\n" when "\n" in a string literal functions the same?

Question

In C# if you do something like string newLine = Environment.NewLine; and inspect the value of newLine you'll find that it is "\r\n". However, if I do something like;

  string[] test = new string[] { "one", "two", "three" };

  Console.WriteLine("With plain slash n:");
  Console.Write(String.Join("\n", test));
  Console.WriteLine("\nWith Environment.NewLine:");
  Console.Write(String.Join(Environment.NewLine, test));

The output is functionally the same.

Why is Environment.NewLine set to \r\n instead of just \n? Doesn't that just make it more difficult to convert from string to character array? Also I read something which led me to believe some input fields don't count Environment.NewLine as two characters which could cause problems if your backing fields are restricted to the length of the input field. Are there any positive reasons for it? Is it just legacy cruft at this point?

Answer 1

The point of Environment.NewLine is to return the newline character for the platform. Presumably for implementations of the .NET framework atop Linux or Unix, it would return just \n.

Answer 2

"New line" in windows/dos is, by convention, CR+LF ("\r\n", "\x0D\x0A"). In the *nix world, "new line" is, by convention, a single LF character ("\n","\0A"). In the pre-OS X Macintosh world, "new line" is, again by convention, a single LF character ("\r","\x0D"). Toss IBM mainframes into the mix and its worse: EBCDIC control character set comprises CR, LF and a specific NL control character.

The reason for this is historical and has to do with the fact that ASCII doesn't have an actual NL (new line) control character: it just has CR (carriage return) and LF (line feed). The various OSes were developed with different printing terminals, and their interpretation of the meaning of these control characters, on which the various operating systems were developed and you have your newline schism.

The CLR I/O system tries to follow Postel's Law ("Be generous in what you accept and strict in what you emit") and so is agnostic on input WRT new line conventions. Consequently, the standard CLR TextReader implementations accept any of CR+LF, CR or LF as constituting a new line indicator. However, on output, WriteLine(), by default, appends the value of `Environment.NewLine'.