using System;

using System.Text.RegularExpressions;

public class Program

{

    public static void Main()

    {

        string orig = "hello_{new}";

        string replacement = "there $& I am $0 being replaced";

        var newStrA = Regex.Replace(orig, "{new}", replacement);

        Console.WriteLine("Regex Replace with $& and $n:");

        Console.WriteLine($"\t{newStrA}");

        Console.WriteLine();

        var newStrB = Regex.Replace(orig, "{new}", replacement.Replace("$", "$$"));

        Console.WriteLine("Regex Replace with escaped $& and $n:");

        Console.WriteLine($"\t{newStrB}");

        Console.WriteLine();

    }

}