public static string FileName = "test.txt";
public static void Main()
string [] lines = {"<!DOCTYPE html>",
" <h1>This is <b>bold</b> heading</h1>",
" <p>This is <u>underlined</u> paragraph</p>",
" <h2>This is <i>italic</i> heading</h2>",
FileName.ToFileInfo().WriteAllLines(lines);
var allLines = FileName.ToFileInfo().ReadAllLines();
foreach(string line in allLines)