Question

In this implementation does hand will be evaluated each time and return another list ?

foreach (Card card in hand.Cards)
{ 

}

Should we replace the above implementation with the following?

var cards = hand.Cards;
foreach (Card card in cards)
{ 

} 

Answer 1

No. Actually the two snippets result in the same code.
In the snippet below:

foreach (Card card in hand.Cards)
{ 

}

hand.Cards is going to be called only once.

Edit:

I’ve created a small snippet, that I hope will show that there is no difference at all:

void Main()
{
    Hand hand = new Hand();
    foreach( var card in hand.Cards() )
    {
        Console.WriteLine("{0}", card);
    }

    var allCards = hand.Cards();
    foreach( var anotherCard in allCards )
    {
        Console.WriteLine("{0}", anotherCard);
    }
}

public class Card
{
private string _cardName;
public Card( string cardName )
    {
        this._cardName = cardName;
    }

    public override string ToString()
    {
        return this._cardName;
    }
}

public class Hand
{
    public IEnumerable<Card> Cards()
    {
        yield return new Card("Ace");
        yield return new Card("King");
    }
}

The otuput (for both methods) is as follows:

Ace
King
Ace
King