newline character replacement in a string?

I have a string in tstring. It’s in the form of A,B,C,D,E,F

I want to replace the commas with returns.
So I use

tstring = tstring.Replace(",",System.Environment.NewLine);

I write this string to file with:

var fileName = "save.txt";
var fw = new StreamWriter(Application.dataPath + "/data/" + fileName);
fw.Write (tstring);
fw.Close();

When I open save.txt it reads ABCDEF

I’ve tried replacing with "
" instead, but with the same result. Any ideas and help appreciated!

Ah, love it when I’m able to answer my own question.
My string tstring was an array.
I just needed to join it together with

var finalsavedata = Array(mysavedata).Join(System.Environment.NewLine);

When I write the file now, I get what I expected:

A

B

C

D

E

F