using System;

public class Program

{

    public static void Main()

    {

        var input = "test1\ntest2\\n\\\\test3";

        var escaped = input.Replace("\\", "\\\\").Replace("\n", "\\n");

        var guid = Guid.NewGuid().ToString();

        var unescaped = escaped.Replace("\\\\", guid).Replace("\\n", "\n").Replace(guid, "\\\\");

​

        Console.WriteLine(input);

        Console.WriteLine("===================================================================");

        Console.WriteLine(escaped);

        Console.WriteLine("===================================================================");

        Console.WriteLine(unescaped);

    }

}