Get the value of treenode which are checked in.net

List<string> PermissionId = new List<string>();


 private string CallNodesSelector()
        {
            TreeNodeCollection nodes = this.TreeView1.Nodes;
            foreach (TreeNode n in nodes)
            {
                GetNodeRecursive(n);
            }
            List<string> distinctPermissionIds = PermissionId.Distinct().ToList();
            string PermissionIds = "1,";
            foreach (string value in distinctPermissionIds)
            {
                PermissionIds += value + ",";
            }
            PermissionIds = PermissionIds.Substring(0, PermissionIds.Length - 1);
            return PermissionIds;

        }

        private void GetNodeRecursive(TreeNode treeNode)
        {
            if (treeNode.Checked == true)
            {
                if (treeNode.Parent != null)
                {
                    TreeNode NodeParent = treeNode.Parent;
                    if (NodeParent.Checked)
                    {

                    }
                    else
                    {
                        PermissionId.Add(NodeParent.Value);
                    }
                }
                string Text = treeNode.Text;
                PermissionId.Add(treeNode.Value);

            }
            foreach (TreeNode tn in treeNode.ChildNodes)
            {
                GetNodeRecursive(tn);
            }

        }