GRIDVIEW WITH TREEVIEW AND CALLBACK

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using WebApplication2.Datas;
using WebControlLibrary1;
using System.Text; 

namespace WebApplication2
{
    public partial class GridTreeView : System.Web.UI.Page, ICallbackEventHandler
    {
        private const string connectionString = @"Data Source=FREDZOOL\SQLEXPRESS;Initial Catalog=DB2008;Integrated Security=True";

        private string result = "mon resultat";
        private readonly int LEVEL_COLUMN_INDEX = 3;
        private readonly int EXPANDABLE_COLUMN_INDEX = 4;


        protected void Page_Load(object sender, EventArgs e)
        {

            if (!IsPostBack)
            {
                MyDatasDataContext context = new MyDatasDataContext();

                var datas = from d in context.Organizations
                            select d;

                GridView1.DataSource = datas;
                GridView1.DataBind();
            }
        }

        protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
        {
            TreeViewButton img = e.Row.FindControl("TreeViewButton1") as TreeViewButton;
            Label monLabel = e.Row.FindControl("monLabel") as Label;

            //on definit les index des colonnes level et expandable que l'on va masquer
            e.Row.Cells[LEVEL_COLUMN_INDEX].Style["visibility"] = "hidden";
            e.Row.Cells[EXPANDABLE_COLUMN_INDEX].Style["visibility"] = "hidden";

            if (img != null)
            {
                Organization d = e.Row.DataItem as Organization;
                img.RowIndex = e.Row.RowIndex;
                img.DestinationControl = ((GridView)sender).ClientID;

                //niveau 0 on ne met pas d'image
                if (d.Level == 0)
                {
                    img.ImageUrl = "";
                    img.Style["visibility"] = "hidden";
                    return;
                }
                img.Style["margin-left"] = string.Format("{0}px", (d.Level * 20));

                //niveau 1 on met un plus
                if (d.Level == 1)
                {
                    img.ImageUrl = img.PlusImg;
                    return;
                }

                //on cache les autres lignes
                img.Style["visibility"] = "hidden";
                img.Style["display"] = "none";

                //les lignes superieurs dont le level est superieur à 0
                //et n'est pas expandable on met l'image railroad
                if (d.Level > 1)
                {
                    if (d.Expandable == false)
                        img.ImageUrl = img.RailroadImg;
                    e.Row.Style["display"] = "none";
                    img.Style["margin-left"] = string.Format("{0}px", (d.Level * 20));
                }
            }
        }

        #region ICallbackEventHandler Members

        public string GetCallbackResult()
        {
            return result;
        }

        public void RaiseCallbackEvent(string eventArgument)
        {
            result = eventArgument; ;
        }

        #endregion

        protected void GridView1_Disposed(object sender, EventArgs e)
        {

        }

        protected void GridView1_DataBound(object sender, EventArgs e)
        {
            GridView1.HeaderRow.Cells[LEVEL_COLUMN_INDEX].Style["visibility"] = "hidden";
            GridView1.HeaderRow.Cells[EXPANDABLE_COLUMN_INDEX].Style["visibility"] = "hidden";
            //GridView1.Columns[EXPANDABLE_COLUMN_INDEX].Style["visibility"] = "hidden";
        }
    }
}