AStarPathFinding.AStar.AddAdjacentCellToOpenList C# (CSharp) Метод

        private void AddAdjacentCellToOpenList(Node parentNode, int columnOffset, int rowOffset, int gCost)
        {
            var adjacentCellIndex = _map.GetAdjacentCellIndex(parentNode.CellIndex, columnOffset, rowOffset);

            // ignore unwalkable nodes (or nodes outside the grid)
            if (adjacentCellIndex == -1)
                return;

            // ignore nodes on the closed list
            if (_closedList.Any(n => n.CellIndex == adjacentCellIndex))
                return;

            var adjacentNode = _openList.SingleOrDefault(n => n.CellIndex == adjacentCellIndex);
            if (adjacentNode != null)
            {
                if(parentNode.G + gCost < adjacentNode.G)
                {
                    adjacentNode.Parent = parentNode;
                    adjacentNode.G = parentNode.G + gCost;
                    adjacentNode.F = adjacentNode.G + adjacentNode.H;
                }

                return;
            }

            var node = new Node(adjacentCellIndex, parentNode) { G = gCost, H = _map.GetDistance(adjacentCellIndex, _map.TargetCell) };
            node.F = node.G + node.H;
            _openList.Add(node);
        }