AIsOfCatan.GameController.BuildFirstRoad C# (CSharp) Method

        public GameState BuildFirstRoad(Player player, Edge edge)
        {
            if (board.GetRoad(edge) != -1)
                throw new IllegalBuildPositionException("The chosen position is occupied by another road");
            if (!board.CanBuildRoad(edge))
                throw new IllegalBuildPositionException("The chosen position is not valid");

            player.RoadsLeft--;
            board = board.PlaceRoad(edge, player.Id);
            return CurrentGamestate();
        }

 /// <summary>
 /// Build a road on the board
 /// If you try to build at a position not connected to the newly placed settlement an IllegalBuildPositionException is thrown
 /// If you try to build more than one road an IllegalActionException is thrown
 /// </summary>
 /// <param name="firstTile">The first tile that the road will be along</param>
 /// <param name="secondTile">The second tile that the road will be along</param>
 public void BuildRoad(Edge edge)
 {
     if (roadBuilt)
     {
         throw new IllegalActionException("Only one road may be built in a turn during the startup");
     }
     if (!settlementBuilt)
     {
         throw new IllegalActionException("The settlement must be placed before the road");
     }
     int[] array = new int[] { settlementPosition.FirstTile, settlementPosition.SecondTile, settlementPosition.ThirdTile };
     if (!(array.Contains(edge.FirstTile) && array.Contains(edge.SecondTile)))
     {
         throw new IllegalBuildPositionException("The road must be placed next to the settlement");
     }
     roadPosition = edge;
     controller.BuildFirstRoad(player, edge);
     roadBuilt = true;
 }