Implementing custom Tree Navigator

Hello! 

I'm working on creation custom plug-in on ASP.NET for eB Web.
This plug-in should show a hierarchy of some types of elements in our company. So, we have some presentations about Navigator Types in your system, and we used  class which implements IPagedDataSource to get data of our tree. We tried to display the tree, but stacked into a problem. Here is a code of class for tree displaying. 

 public partial class VNPNavigatorTest : ActivityUserControl {
        protected void Page_Load( object sender, EventArgs e ) {
            treeControl.PagedDataSource = new CustomPagedDataSource();
            treeControl.HasRootCheckBox = true;
        }
    }

    public class CustomPagedDataSource : IPagedDataSource {
        private const int ProjectsFolderId = -1;
        eB.Data.Object IPagedDataSource.GetContainer( eBContext context ) {
            HttpContext.Current.Response.Write("<script> alert(\"Container\");</script>");
            return new eB.Data.Object(context.eBSession, ProjectsFolderId, ObjectType.Folder) { Label = "Objects" };
        }

        PagedTreeNodeDataList IPagedDataSource.GetPage( eBContext context, string parentId, int offset, int size ) {
            PagedTreeNodeDataList list = new PagedTreeNodeDataList();
            var session = context.eBSession;
            var objectInfo = new ObjectInfoPair(parentId);
            if (objectInfo.t == ObjectType.Folder) {
                list.Add(new PagedTreeNodeData {
                    Id = new ObjectInfoPair(0, ObjectType.Folder).ToString(),
                    Label = "111",
                    Type = (int)ObjectType.Folder,
                    Flags = 0

                });
            }
            HttpContext.Current.Response.Write("<script> alert(\"Children\");</script>");
            return list;
        }
    }

The first alert function is called, but the second is not. So, why the method GetPage() is not called? Here is a code of tree-page below. 

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="VNPNavigatorTest.ascx.cs" Inherits="VNPTest.VNPNavigatorTest" %>
<%@ Register TagPrefix="eB" Namespace="eB.Web.UI.Controls.Tree" Assembly="eB.Library.Web" %>

<div class="treePanel">

      <eB:PagedTreeControl runat="server" ID="treeControl"
            ImageUriTemplate="~/Framework/Images/Objects/t{Type}f{Flags}.gif"
            LinkUriTemplate="javascript:OnTreeNodeClicked('{Id}')"
            LinkUriTarget="" />
</div>

And here is a code of AppElements.config.

<?xml version="1.0"?>
<eBPlugIn id="VNPTest" helpUri="~/PlugIns/VNPTest/Help" resources="VNPTest.Properties.Resources,VNPTest" >

  <Types>
    <Type id="NavigationProvider" type="eB.Web.Core.Elements.Navigation.NavigationProvider,eB.Library.Web"/>
    <Type id="SearchProvider" type="eB.Web.Core.Elements.Searching.SearchProvider,eB.Library.Web"/>
    <Type id="WebControlNavigationProvider" type="eB.Web.Core.Elements.Navigation.WebControlNavigationProvider,eB.Library.Web"/>
    <Type id="WebSearchProvider" type="eB.Web.Core.Elements.Searching.WebControlSearchProvider,eB.Library.Web"/>
    <Type id="TreeNavigationProvider" type="eB.Web.Core.Elements.Navigation.TreeNavigationProvider,eB.Library.Web"/>
  </Types>
  
  <Objects />

  <Services>
    <NavigationProvider>
      
      <WebControlNavigationProvider Id="Тестовое дерево объектов" ASCX="/PlugIns/VNPTest/VNPNavigatorTest.ascx" />

      <!--<TreeNavigationProvider id="VNPTestNavigation" 
                              RootID="testTreeNavigator" 
                              ExplodeUri="/Plugins/VNPTest/VNPNavigatorTest.aspx" 
                              HomePageUri="" 
                              ImageUri="/Framework/Images" />-->
                              
    </NavigationProvider>

    <SearchProvider>
      <WebSearchProvider Id="Поиск элементов ВНП" TargetObjectType="Document" VisibleToUser="true" ASCX="/PlugIns/VNPTest/MySearch.ascx" AdvancedSearchURI="/PlugIns/Reporting/ReportWizard.aspx?for=94"/>
    </SearchProvider>
    
  </Services>
  
</eBPlugIn>

We also tried to use TreeNavigatorProvider, so it is commented now. 
Could you give us some advices how to implement Tree Navigator in the best way?