1 前台代码:  2 
     
        3 要害是:OnTreeNodeExpanded="TreeView1_TreeNodeExpanded"  4  5 后台代码:  6  7   protected void TreeView1_TreeNodeExpanded(object sender, TreeNodeEventArgs e)  8         {  9             TreeNodeCollection ts = null; 10             if (e.Node.Parent == null) 11             { 12                 ts = ((TreeView)sender).Nodes; 13             } 14             else 15                 ts = e.Node.Parent.ChildNodes; 16             foreach (TreeNode node in ts) 17             { 18                 if (node != e.Node) 19                 { 20                     node.Collapse(); 21                 } 22             } 23         } 24 -