using System;

​

public record Foo(string? Bar);

​

public class Program

{

    public static void Main()

    {

        Foo foo = new(null);

        var fooWithBar = foo with { Bar = "baz" };

​

        Console.WriteLine($"foo.Bar = {foo.Bar}\nfooWithBar.Bar = {fooWithBar.Bar}");

    }

}