using System;

​

public class Program

{

    public static void Main()

    {

        ShopperTicket shopperTicket = null;

        if (IfCondition(shopperTicket))

            Console.WriteLine("Entrou no IF");

        else 

            Console.WriteLine("Não entrou no IF");

    }

    public static bool IfCondition(ShopperTicket shopperTicket) {

        return !shopperTicket?.IsAuthenticated ?? false;

    }

}

​

public class ShopperTicket {

    public ShopperTicket(bool isAuthenticated) {

        IsAuthenticated = isAuthenticated;

    }

    public bool IsAuthenticated { get; }

}