using System;

​

public class Program

{

    public static void Main()

    {

        var userService = new UserService();

        Console.WriteLine(userService.AddUser("FirstName", "LastName", 20));

    }

}

​

public class UserService

{

    public bool AddUser(string firstName, string lastName, int age)

    {

        if (string.IsNullOrWhiteSpace(firstName) || string.IsNullOrWhiteSpace(lastName))

        {

            return false;

        }

​

        var drinkingAge = 21;

        var canDrink = false;

        if (age >= drinkingAge)

        {

            canDrink = true;

        }

​

        var user = new User

        {

            Name = firstName + " " + lastName, 

            Age = age, 

            IsOfDrinkingAge = canDrink

        };

        return UserData.AddUser(user);

    }

}

​

public class User

{

    public string Name { get; set; }

​

    public int Age { get; set; }

​

    public bool IsOfDrinkingAge { get; set; }

}

​

public static class UserData

{

    public static bool AddUser(User person)

    {

        return true;

    }

}