前台代码:<asp:TreeView ID="TreeView1" runat="server" ExpandDepth="0" OnTreeNodeExpanded="TreeView1_TreeNodeExpanded" ShowLines="True">要害是:OnTreeNodeExpanded="TreeView1_TreeNodeExpanded"后台代码:  protected void TreeView1_TreeNodeExpanded(object sender, TreeNodeEventArgs e)        {            TreeNodeCollection ts = null;            if (e.Node.Parent == null)            {                ts = ((TreeView)sender).Nodes;            }            else                ts = e.Node.Parent.ChildNodes;            foreach (TreeNode node in ts)            {                if (node != e.Node)                {                    node.Collapse();                }            }        }