asp.net中treeview的使用

protected   void   treeviewProductDataBind()   
  {   
      SqlConnection   cn   =   new   SqlConnection("server=192.168.1.227;database=Northwind;user id=sa;password=;");   
      SqlDataAdapter   daCategories   =   new   SqlDataAdapter("select   CategoryID,CategoryName   from   Categories",   cn);   
      DataSet   dsCategories   =   new   DataSet();   
      daCategories.Fill(dsCategories);   
      SqlDataAdapter   daProducts   =   new   SqlDataAdapter("select   ProductID,ProductName,CategoryID   from   Products",   cn);   
      DataSet   dsProducts   =   new   DataSet();   
      daProducts.Fill(dsProducts);   
      int   CategoriesCount   =   dsCategories   .Tables   [0].Rows   .Count   ;   
      int   ProductsCount   =   dsProducts.Tables[0].Rows.Count;   
      for(int i=0;i< CategoriesCount;i++)   
      {   
          TreeNode   treenodeParent   =   new   TreeNode();   
          treenodeParent.Text   =   dsCategories.Tables[0].Rows[i]["CategoryName"].ToString();   
          treenodeParent.Value   =   dsCategories.Tables[0].Rows[i]["CategoryID"].ToString();
          treenodeParent.ImageUrl = "folder.gif";
          //treenodeParent.NavigateUrl   =   "";   
          //treenodeParent.Target   =   "";   
          this.treeviewProduct.Nodes.Add(treenodeParent);   
          for   (int   j   =   0;   j   <   ProductsCount;   j++)   
          {   
              if   (dsCategories.Tables[0].Rows[i]["CategoryID"].ToString()   ==   dsProducts.Tables[0].Rows[j]["CategoryID"].ToString())   
              {   
                      TreeNode   treenodeChild   =   new   TreeNode();
                      treenodeChild.Text   =   dsProducts.Tables[0].Rows[j]["ProductName"].ToString();   
                      treenodeChild.Value   =   dsProducts.Tables[0].Rows[j]["ProductID"].ToString();
                      treenodeChild.ImageUrl = "word.gif";
                      //treenodeChild.NavigateUrl   =   "";   
                      //treenodeChild.Target   =   "";   
                      treenodeParent.ChildNodes.Add(treenodeChild);   
              }   
          }
      }   
  }
  protected   void   treeviewProduct_TreeNodeExpanded(object   sender,   TreeNodeEventArgs   e)   
  {   
      foreach   (TreeNode   treenode   in   this.treeviewProduct.Nodes)   
      {   
          if   (treenode.Value   !=   e.Node.Value)   
          {   
                  treenode.CollapseAll();
          }
          else
          {
              treenode.ImageUrl = "folderopen.gif";
          }
      }   
  }  
//前台页面
<asp:TreeView ID="treeviewProduct" runat="server" ShowLines="true" Font-Size="12px" ExpandDepth="0" OnTreeNodeExpanded="treeviewProduct_TreeNodeExpanded" CollapseImageUrl="folder.gif" ExpandImageUrl="folderopen.gif">   
</asp:TreeView>