treeview递归绑定节点

private void AppendChild(TreeNode tnParent, string pvarid)
{

DataRow[] drs = dtData.Select("substring(str_VarID,1," + pvarid.Length + ")=" + pvarid + " and len(str_VarID)=" + pvarid.Length + "+3");
foreach (DataRow dr in drs)
{
TreeNode tn = new TreeNode();
tn.Text = dr["str_Name"].ToString();
tn.Expanded = false;
tn.NavigateUrl = dr["str_Url"].ToString();
AppendChild(tn, dr["str_VarID"].ToString());
tnParent.ChildNodes.Add(tn);
}
}