first one

// What will be the output in console?
using System;

public class User
{
    public string Name { get; }
    public User(string name)
    {
        this.Name = name;
    }
}

public class Program
{
    public static void ChangeUser(User u)
    {
        u = new User("User 2");
    }

    public static void Main()
    {
        var user = new User("User 1");
        ChangeUser(user);

        Console.WriteLine(user.Name);
    }
}