c＃：在扩展方法中访问对象属性

Question

I'm currently writing ac# Rummikub game.

I have an object named Card that has Value and Color properties. Also, inside Player 's Class, I have a list of cards (player's hand).

In the Player class, I wrote some methods that get only the player's hand as parameter. stuff like:

  // Determines what card should the CPU throw. public int CardToThrow(List<Card> CPUHand). // Call: int cardToThrow = Player1.CardToThrow(Player1.Hand); 

I want to be able to call the function like this:

  int cardToThrow = Player1.Hand.CardToThrow(); 

When I tried to write the Extension Method, I didn't manage to acces the card's properties:

 public static class HandExtensionMethods { public static int foo<Card>(this List<Card> list) { return list[0].Value; } } 

Error:

'Card' does not contain a definition for 'Value' and no extension method 'Value' accepting a first argument of type 'Card' could be found (are you missing a using directive or an assembly reference?)

How should I write the extension methods so I could access the object properties?

Answer 1

Your extension method is generic with a parameter type of Card which is shadowing the concrete Card class. Remove the generic parameter:

public static int foo(this List<Card> list)
{
    return list[0].Value;
}