private void tvDevice_BeforeExpand(object sender, TreeViewCancelEventArgs e)
        {
           if (e.Action != TreeViewAction.Unknown)
           {
              //这里循环折叠其余节点
           }
         }

------解决方案--------------------

C# code

        protected void TreeView1_SelectedNodeChanged(object sender, EventArgs e)
        {
            //TreeView1.SelectedNode.ToggleExpandState();
            TreeView1.CollapseAll();
            TreeView1.SelectedNode.Expand();

            TreeNode node = TreeView1.SelectedNode;
            while (node.Parent != null)
            {
                node.Parent.Expand();
                node = node.Parent;
            }
        }

------解决方案--------------------
C# code

  protected void Treeview1_TreeNodeExpanded(object sender, TreeNodeEventArgs e)
    {
        if (e.Node.Depth != 0)
        { 
            foreach (TreeNode item in Treeview1.Nodes)
            {
                if (e.Node.Value == item.Value)
                {
                    item.Expand();
                }
                else
                {
                    item.Collapse();
                }
            }
        }
    }