使用JavaScript展开/折叠TreeView中所有节点(Expand and Collapse All Nodes of asp.net Treeview on the client with javascript)

代码如下，国外网站上copy很多，也不知道谁才是原作者，但在.net 3.5下好像有一点毛病，就是图标的问题，不知道如何解决：

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="jstree.aspx.cs" Inherits="jstree" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title>Untitled Page</title>

    <script type="text/javascript">

    function expandAll(treeViewId)
    {
         var treeView = document.getElementById(treeViewId);
         var treeLinks = treeView.getElementsByTagName("a");
         var j = true;
         for(i=0;i<treeLinks.length;i++)
         {
              if(treeLinks[i].firstChild.tagName == "IMG")
              {
                var node = treeLinks[i];
                var level = parseInt(treeLinks[i].id.substr(treeLinks[i].id.length - 1),10);
                var childContainer = document.getElementById(treeLinks[i].id + "Nodes");

               if(j)
                {
                    if(childContainer.style.display == "none")
                    TreeView_ToggleNode(eval(treeViewId +"_Data"),level,node,'r',childContainer);
                    j = false;
                }
                else
                {
                    if(childContainer.style.display == "none")
                    TreeView_ToggleNode(eval(treeViewId +"_Data"),level,node,'l',childContainer);
                }
              }
          }
    }


    function collapseAll(treeViewId)
    {
         var treeView = document.getElementById(treeViewId);
         var treeLinks = treeView.getElementsByTagName("a");
         var j = true;
         for(i=0;i<treeLinks.length;i++)
         {
              if(treeLinks[i].firstChild.tagName == "IMG")
              {
                var node = treeLinks[i];
                var level = parseInt(treeLinks[i].id.substr(treeLinks[i].id.length - 1),10);
                var childContainer = document.getElementById(treeLinks[i].id + "Nodes");

               if(j)
                {
                    if(childContainer.style.display == "block")
                    TreeView_ToggleNode(eval(treeViewId +"_Data"),level,node,'r',childContainer);
                    j = false;
                }
                else
                {
                    if(childContainer.style.display == "block")
                    TreeView_ToggleNode(eval(treeViewId +"_Data"),level,node,'l',childContainer);
                }
              }
          }
   }

    function Button1_onclick() {
        expandAll('<%=TreeView1.ClientID%>');
    }

    function Button2_onclick() {
        collapseAll('<%=TreeView1.ClientID%>');
    }

    </script>

</head>
<body>
    <form id="form1" runat="server">
    <div>
    </div>
    <asp:TreeView ID="TreeView1" runat="server">
        <Nodes>
            <asp:TreeNode Text="New Node" Value="New Node">
                <asp:TreeNode Text="New Node" Value="New Node">
                    <asp:TreeNode Text="New Node" Value="New Node">
                        <asp:TreeNode Text="New Node" Value="New Node"></asp:TreeNode>
                    </asp:TreeNode>
                </asp:TreeNode>
                <asp:TreeNode Text="New Node" Value="New Node"></asp:TreeNode>
                <asp:TreeNode Text="New Node" Value="New Node">
                    <asp:TreeNode Text="New Node" Value="New Node">
                        <asp:TreeNode Text="New Node" Value="New Node"></asp:TreeNode>
                    </asp:TreeNode>
                </asp:TreeNode>
                <asp:TreeNode Text="New Node" Value="New Node"></asp:TreeNode>
                <asp:TreeNode Text="New Node" Value="New Node"></asp:TreeNode>
                <asp:TreeNode Text="New Node" Value="New Node">
                    <asp:TreeNode Text="New Node" Value="New Node"></asp:TreeNode>
                </asp:TreeNode>
            </asp:TreeNode>
        </Nodes>
    </asp:TreeView>
    </form>
    <p>
        <input id="Button1" type="button" value="Expand All" onclick="return Button1_onclick()" /></p>
    <p>
        <input id="Button2" type="button" value="Collapse All" onclick="return Button2_onclick()" /></p>
</body>
</html>