递归为TreeView控件添加节点

private void BindTreeNode(string cityNo, TreeNodeCollection nodes,int level)
{
      IEnumerable<AreaTInfo> CityList = areaList.Where(ati => ati.F_AreaSN == cityNo);
      foreach (AreaTInfo ati in CityList)
      {
           TreeNode tn = new TreeNode(ati.AreaName);
           tn.Tag = ati.AreaSN;
           int templevel = level+1;
           BindTreeNode(ati.AreaSN, tn.Nodes,level);
           if (level == 0)
           {
               tn.Expand();
           }
           nodes.Add(tn);
      }
}