用了Treeview控件后生成了无限循环树，怎么改？

private void bind_treeview1(int id, TreeNode tn)
{
string sql = "select * from FLB where LSLB=" + id.ToString() + " order by LBMC";
DataTable dt = new DataTable();
dt = SX.mydb.GET_DataTable(sql);
for (int i = 0; i <= dt.Rows.Count - 1; i++)
{
if (tn == null)
{
TreeNode mytreenode = new TreeNode();
mytreenode.Text = dt.Rows[i]["LBMC"].ToString();
mytreenode.Tag = dt.Rows[i]["FLID"].ToString();
mytreenode.Expand();
treeView1.Nodes.Add(mytreenode);
bind_treeview1(Convert.ToInt32(dt.Rows[i]["FLID"].ToString()), mytreenode);
}
else
{
TreeNode mytn = new TreeNode();
mytn.Text = dt.Rows[i]["LBMC"].ToString();
mytn.Tag = dt.Rows[i]["FLID"].ToString();
mytn.Expand();
tn.Nodes.Add(mytn);

}
}

}

要看你的代码上是怎么用的！如果你在使用时使用的循环控制那可能会出现你说的无限循环树！看看的生成树代码！