TreeNode tn = treeView1.SelectedNode;
            int i = tn.Index;
            TreeNodeCollection tc = tn.Parent == null ? treeView1.Nodes : tn.Parent.Nodes;
            if ((i == 0 && Direction==1)||(i == tc.Count - 1 && Direction==-1))
            {
                   ///
                   /// Заглушка
                   ///
            }
            else
            {
                TreeNode temp = tn;
                tc[i] = tc[i - Direction];
                tc[i - Direction] = temp;
                treeView1.SelectedNode = tc[i - Direction];
            }