Passing Arraylist

Question

I am modifying a Blackjack game program I got from from one of my Deitel C# books. I want to use objects for the cards. There is a Windows forms program and a Web service program. The web service creates the deck of cards in one method. Then a second method returns a card object one at a time for the player and the dealer. A third method recevies a arraylist of card objects to tabulate totals from the Windows form program. The problem arises in the Windows form program. I am trying to pass a arraylist of card objects to the service. The windows form program won't compile because it says it can't convert an arraylist to an object array even though my method definition in the service declares the parameter as an arraylist.  Any help would be appreciated. Stumped in Chicago.