TreeView to database or at least DataTable

[Aleksandr]

The main question how to fully traverse/circumvent through all TreeView, for transforming Tree structure into a Table structure.
I want to note that the TreeView may contain a different number of branches, with different depths and different names.
I found a lot of information how to populate TreeView e.g. from DataTable, but I didn’t found information how to recursively traverse/circumvent a TreeView and populate/fill data e.g. to DataTable.

As sample I have following TreeView:
Aaron
-Baldwin
--Caleb
---Dale
--Earl
-Fabian
Gabriel
-Harold
-Ian

Necessary to convert the TreeView into e.g. DataTable:
id | Name | ParentId
--------------------------------
1 | Aaron | null
2 | Baldwin | 1
3 | Caleb | 2
4 | Dale | 3
5 | Earl | 2
6 | Fabian | 1
7 | Gabriel | null
8 | Harold | 7
9 | Ian | 7

[Aleksandr]

Following code is work well:

private void buttonSave_Click(object sender, EventArgs e)
        {
            TraverseTreeView(treeView1);
            string temp = String.Empty;
            foreach (string str in name)
                temp += str + Environment.NewLine;
            MessageBox.Show(temp);
            name.Clear();
        }
        List<string> name = new List<string>();
        private void TraverseTreeView(TreeView tview)
        {
            TreeNode temp = new TreeNode();
            for (int k = 0; k < tview.Nodes.Count; k++)
            {
                temp = tview.Nodes[k];
                name.Add(k+"\t"+temp.Text+"\tnull");
                for (int i = 0; i < temp.Nodes.Count; i++)
                    visitChildNodes(temp.Nodes[i]);
            } 
        }
        private void visitChildNodes(TreeNode node)
        {
            name.Add(node.Text);
            for (int j = 0; j < node.Nodes.Count; j++)
                visitChildNodes(node.Nodes[j]);
        }

But there is still several things that I don't know how to realize:
1. Do not use global variable (List<string> name) for collecting result;
2. Correctly collect data perhaps in DataTable, in format "1 | Aaron | null".
Please chech code below, and fix mistaks:

private void buttonSave_Click(object sender, EventArgs e)
        {
            DataTable dt = new DataTable();
            dt = TraverseTreeView(treeView1);
            string temp = String.Empty;
            foreach (string str in dt)
                temp += str + Environment.NewLine;
            MessageBox.Show(temp);
            dt.Clear();
        }
        //List<string> name = new List<string>();
        private DataTable TraverseTreeView(TreeView tview)
        {
            DataTable dt = new DataTable();
            dt.Columns.Add("id", typeof(int));
            dt.Columns.Add("Name");
            dt.Columns.Add("ParentId", typeof(int));
            TreeNode temp = new TreeNode();
            for (int k = 0; k < tview.Nodes.Count; k++)
            {
                temp = tview.Nodes[k];
                dt.Rows.Add(k, temp.Text, null);
                //name.Add(temp.Text);
                for (int i = 0; i < temp.Nodes.Counst; i++)
                    dt.Rows.Add(i, visitChildNodes(temp.Nodes[i]).Text, i - 1);
            }
            return dt;
        }
        private DataTable visitChildNodes(TreeNode node)
        {
            //name.Add(node.Text);
            DataTable dt = new DataTable();
            dt.Columns.Add("id", typeof(int));
            dt.Columns.Add("Name");
            dt.Columns.Add("ParentId", typeof(int));
            for(int j = 0; j < node.Nodes.Count; j++)
                dt.Rows.Add(j, visitChildNodes(node.Nodes[j]).Text, j - 1);
            return dt;
        }