using System;

​

public class Program

{

    static void Main(string[] args)

    {

        var person = Person;

        DoS(Person);

        Console.WriteLine("{0}, {1}, {2}", person.Id, person.FirstName, person.LastName[0]);

        LogName(Person);

    }

​

    static (int Id, string FirstName, string[] LastName) Person = (Id: 1, FirstName: "Bill", LastName: new[] { "Gates" });

    public static void DoS((int Id, string FirstName, string[] LastName) obj) {

        obj.LastName[0] = "Lama";;

    }

    public static void LogName((int Id, string FirstName, string[] LastName) obj) {

            Console.WriteLine("{0}, {1}, {2}", obj.Id,obj.FirstName, obj.LastName[0]);

    }

}