VisualUIAVerify.Controls.AutomationElementTreeNode.AddChildrenNodesToTreeNodeInternal C# (CSharp) Method

        private void AddChildrenNodesToTreeNodeInternal(ICollection<TreeNode> childrenNodes, bool clearChildrenCollection, bool onlyInsertNew)
        {
            Debug.Assert(!this.AutomationElementTreeControl.InvokeRequired, "this method can run only on IUThread!");

            //this is used to mark which node is new (and will be inserted) and
            //which is obsolete(and will be removed)
            bool[] newNodeFlags = new bool[childrenNodes.Count]; //true means new
            bool[] obsoleteNodesFlags = new bool[this.TreeNode.Nodes.Count]; //true means obsolete

            //lets mark all new children nodes new
            for (int k = 0; k < newNodeFlags.Length; k++)
                newNodeFlags[k] = true;

            //lets mark all old children nodes obsolete
            for (int k = 0; k < obsoleteNodesFlags.Length; k++)
                obsoleteNodesFlags[k] = true;

            //if we are not going to clear the collection and we have some old and some new nodes
            if (!clearChildrenCollection && childrenNodes.Count > 0 && this.TreeNode.Nodes.Count > 0)
            {
                //lets compare old nodes with new nodes and set flags which nodes should be inserted and which 
                //should be removed
                int i = 0;
                foreach (TreeNode newNode in childrenNodes)
                {
                    AutomationElement newElement = TreeHelper.GetNodeElement(newNode);

                    for (int j = 0; j < this.TreeNode.Nodes.Count; j++)
                    {
                        TreeNode oldNode = this.TreeNode.Nodes[j];
                        AutomationElement oldElement = TreeHelper.GetNodeElement(oldNode);

                        if (newElement == oldElement)
                        {
                            newNodeFlags[i] = false;
                            obsoleteNodesFlags[j] = false;
                        }
                    }
                    i++;
                }
            }

            if (!onlyInsertNew)
            {
                //lets remove all obsolete nodes
                for (int i = 0, j = 0; i < obsoleteNodesFlags.Length; i++, j++)
                {
                    //i is used to iterate thru flags array
                    //j is used to iterate thru nodes collection

                    if (obsoleteNodesFlags[i] || clearChildrenCollection)
                    {
                        //this will decrement index of all nodes after j-node
                        this.TreeNode.Nodes[j].Remove();
                        j--;
                    }
                }
            }

            //lets go and insert new nodes
            int l = 0;
            foreach (TreeNode newNode in childrenNodes)
            {
                if (newNodeFlags[l])
                {
                    this.TreeNode.Nodes.Insert(Math.Max(0, Math.Min(l, this.TreeNode.Nodes.Count - 1)), newNode);
                }
                l++;
            }
        }