Tree View Control Office Sharepoint 2007

I am using the code:
using System;
using System.Runtime.InteropServices;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Serialization;

using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;
using Microsoft.SharePoint.WebPartPages;
using System.ComponentModel;
using System.Collections.Generic;
using System.Text;
using System.Reflection;

namespace LibraryTree
{

[Guid("f77a9774-a3cb-4020-a9ff-01bf2485a29d")]
public class LibraryTree : Microsoft.SharePoint.WebPartPages.WebPart
{

public LibraryTree()
{
this.Title = "Document Library Tree View";
this.ExportMode = WebPartExportMode.All;
}

protected string _LibraryPath = "";
[Personalizable(PersonalizationScope.Shared),
Browsable(false),
Category("Document Library Selection")]
public string LibraryPath
{
get
{
return _LibraryPath;
}
set
{
_LibraryPath = value;
}
}

public override ToolPart[] GetToolParts()
{
List<toolpart> parts = new List<toolpart>();
PickerToolPart picker = new PickerToolPart();
parts.AddRange(base.GetToolParts());
picker.Items.Add(new PickerItem("Document Library To View:", "LibraryPath", PickerType.List));
picker.Title = "Document Library Selection";
parts.Add(picker);
return parts.ToArray();
}

protected override void CreateChildControls()
{
base.CreateChildControls();
SPWeb wb = SPContext.Current.Web;
string baseURL = wb.Url.ToString();
string _CorrectedLibraryPath;
try
{
if (_LibraryPath == "")
{
throw new Exception("No Document Library selected. Please select one from web part properties pane.");
}

//check if the library name was selected from picker or entered manually
if (_LibraryPath.Substring(0, 1) == "/")
{
_CorrectedLibraryPath = _LibraryPath.Substring(1);
}
else
{
_CorrectedLibraryPath = _LibraryPath;
}

SPDocumentLibrary doclib = (SPDocumentLibrary)wb.Lists[_CorrectedLibraryPath];

// A table for layout
Table tbl;
TableRow row;
TableCell cell;
tbl = new Table();
row = new TableRow();
cell = new TableCell();

// first row for title
cell.VerticalAlign = VerticalAlign.Middle;
cell.HorizontalAlign = HorizontalAlign.Left;
Label lblTitle = new Label();
lblTitle.Text = "Tree View of " + doclib.Title +":" ;
cell.Controls.Add(lblTitle);
row.Controls.Add(cell);
tbl.Controls.Add(row);

//second row for treeview
row = new TableRow();
cell = new TableCell();
cell.VerticalAlign = VerticalAlign.Middle;
cell.HorizontalAlign = HorizontalAlign.Left;
TreeView TreeView1 = new TreeView();
SPFolder root = doclib.RootFolder;
TreeNode node = new TreeNode();
node = Utility.GetFolderNode(node, root, baseURL);
node.Text = doclib.Title;
node.NavigateUrl = doclib.DefaultViewUrl;
long size = Utility.GetFolderSize(root) / 1024;
long numFiles = Utility.GetNumberOfFilesInFolder(root);
node.ToolTip = "Size:" + size.ToString() + " KBs " + " Files:" + nu