c＃如何在函数中使用实例化对象的属性（列表）？

Question

I have two classes. A Player Class that has the properties Name, Balance and Cards:

class Player
{
    public string Name;
    public decimal Balance;
    public List<Card> Cards; // My question is related to this property
}

And a Card class:

class Card
{
    public string Name;
    public int Attack;
    public int Defense;
    public decimal Cost;
}

I instantiated an object for the player:

var player = new Player("Ahmad", 100);

and also a card:

var card = new Card("Mino", 3, 3, 200);

then added the card to the player's Cards:

player.Cards[0] = card;

I can simply display it on the main method where it was instantiated but the Problem is : How can I access the player's Cards in a function? like so:

///<summary>
/// Function to show current cards
/// </summary>
public static void ViewCards(object player)
{
    var cards = player.Cards  // This line doesn't work
    foreach (var card in cards)
    {
        Console.WriteLine($"{card.Name}");
        Console.WriteLine($"Attack: {card.Attack}");
        Console.WriteLine($"Defense: {card.Defense}");
        Console.WriteLine($"Cost: ${card.Cost}");
    }    
}

Answer 1

Change the method signature Change the player parameter , from Object to Player

public static void ViewCards(Player player)
{
}

Answer 2

If you want to maintain a more OO approach you could make it a method on the player.

class Player
{
    public string Name {get;set;}
    public decimal Balance {get;set;}
    public List<Card> Cards {get;set;}

    public void ViewCards()
    {
        foreach (var card in Cards)
        {
            Console.WriteLine($"{card.Name}");
            Console.WriteLine($"Attack: {card.Attack}");
            Console.WriteLine($"Defense: {card.Defense}");
            Console.WriteLine($"Cost: ${card.Cost}");
        }    
    }
}

And then on some method

player.ViewCards();

Also you should not use public fields, instead use a Property. This promotes better encapsulation and class cohesiveness. I am referring here to Name , Balance , and Cards . The get; and set; will create a backing field during compile time.

Answer 3

You need to cast the object to class Player

///<summary>
/// Function to show current cards
/// </summary>
public static void ViewCards(object player)
{
    var cards = (player as Player)?.Cards;  // cast object to Player, returs null if object is not of correct type

    if (cards != null)
    {
       foreach (var card in cards)
       { 
           Console.WriteLine($"{card.Name}");
           Console.WriteLine($"Attack: {card.Attack}");
           Console.WriteLine($"Defense: {card.Defense}");
           Console.WriteLine($"Cost: ${card.Cost}");
       }  
    }    
}

Answer 4

If you don't want to specify object type, you can use dynamic

public static void ViewCards(dynamic player)
{
    var cards = player.Cards  // This line doesn't work
    foreach (var card in cards)
    {
        Console.WriteLine($"{card.Name}");
        Console.WriteLine($"Attack: {card.Attack}");
        Console.WriteLine($"Defense: {card.Defense}");
        Console.WriteLine($"Cost: ${card.Cost}");
    }    
}

But you may have an exception on runtime if your object doesn't have a property Cards