namespaces and classes - Organizing your code - There’s an easier way to initialize objects with C#

Head First C#:
A Learner's Guide to Real-World Programming
with C# and .NET
Kindle版

開発環境

Head First C Sharp: A Learner’s Guide to Real-World Programming with C Sharp and .NET (Andrew Stellman(著)、Jennifer Greene(著)、O’Reilly Media)の Chapter 3(namespaces and classes - Organizing your code)、p.181(Exercise)の解答を求めてみる。

コード

Guy.cs

namespace Guys;

internal class Guy
{
    public string? Name;
    public int Cash;

    public void WriteMyInfo()
    {
        Console.WriteLine($"{Name} has {Cash} bucks.");
    }
    public int GiveCash(int amount)
    {
        if (amount <= 0)
        {
            Console.WriteLine($"{Name} says: {amount} isn't a valid amount");
            return 0;
        }
        if (amount > Cash)
        {
            Console.WriteLine($"{Name} says: I don't have enough cash to give you {amount}");
            return 0;
        }
        Cash -= amount;
        return amount;
    }
    public void ReceiveCash(int amount)
    {
        if (amount <= 0)
        {
            Console.WriteLine($"{Name} says: {amount} isn't an amount I'll take");
        }
        else
        {
            Cash += amount;
        }
    }
}

Program.cs

using Guys;

Guy joe = new Guy() { Name = "Joe", Cash = 50 };
Guy bob = new Guy() { Name = "Bob", Cash = 100 };

while (true)
{
    Console.Write("Enter an amount: ");
    string? howMuch = Console.ReadLine();
    if (howMuch == "") return;
    if (int.TryParse(howMuch, out int amount))
    {
        Console.Write("Who should give the cash: ");
        string? whichGuy = Console.ReadLine();
        if (whichGuy == "Joe")
        {
            bob.ReceiveCash(joe.GiveCash(amount));
        }
        else if (whichGuy == "Bob")
        {
            joe.ReceiveCash(bob.GiveCash(amount));
        }
        else
        {
            Console.WriteLine("Plaese enter 'Joe' or 'Bob'");
        }
    }
    else
    {
        Console.WriteLine("Please enter an amount (or a blank line to exit).");
    }
}

入出力結果(Terminal, Zsh)

Enter an amount: 10
Who should give the cash: Joe
Enter an amount: 40
Who should give the cash: Joe
Enter an amount: 1
Who should give the cash: Joe
Joe says: I don't have enough cash to give you 1
Bob says: 0 isn't an amount I'll take
Enter an amount: 150
Who should give the cash: Bob 
Enter an amount: 1
Who should give the cash: bob
Plaese enter 'Joe' or 'Bob'
Enter an amount: Bob
Please enter an amount (or a blank line to exit).
Enter an amount: 1
Who should give the cash: Bob
Bob says: I don't have enough cash to give you 1
Joe says: 0 isn't an amount I'll take
Enter an amount: -1
Who should give the cash: Joe
Joe says: -1 isn't a valid amount
Bob says: 0 isn't an amount I'll take
Enter an amount: