1using System;
 2using System.Collections.Generic;
 3using System.Text;
 4using Ch10CardLib;
 5
 6namespace Ch10CardClient
 7{
 8 class Program
 9 {
10 static void Main(string[] args)
11 {
12 Deck myDeck = new Deck();
13 myDeck.Shuffle();
14 for (int i = 0; i < 52; i++)
15 {
16 Card tempCard = myDeck.GetCard(i);
17 Console.Write(tempCard.ToString());
18 if (i != 51)
19 Console.Write(", ");
20 else
21 Console.WriteLine();
22 }
23 Console.ReadKey();
24 }
25 }
26}

        public Card GetCard(int cardNum)
        {
            if (cardNum >= 0 && cardNum <= 51)
                return cards[cardNum];
            else
                throw (new System.ArgumentOutOfRangeException("cardNum", cardNum, "Value must be between 0 and 51."));
        }

on line 16 Card tempCard = myDeck.GetCard(i);

GetCard return cards[cardNum]

how do you assign value of cards[cardNum] to tempCard? isn't tempCard is the variable type of Card?

If I understand your post correctly, the method GetCard does not return a Cards object. It returns a Card object from within the internal Cards collection of Deck. cards[cardNum] returns a Card object at the position within cards specified by cardNum.

cardNum does not seem to be defined anywhere.