AJAX DataGrid

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

namespace AndrewGolik.DaoTraining.DataAccessLayer 
{
    public abstract class DaoFactory 
    {

        public abstract  CustomerDao  GetCustomerDao();
        public abstract  OrderDao   GetOrderDao();
       

       
       
        public static DaoFactory GetDaoFactory()
        {
            string strDaoFactoryType = ConfigurationManager.AppSettings["DaoFactory"];
            if (String.IsNullOrEmpty(strDaoFactoryType))
                throw new NullReferenceException("DaoFactory type configuration is missing from your web.config.");

            else
            {
                Type DaoFactoryType = Type.GetType(strDaoFactoryType);
                if (DaoFactoryType == null)
                    throw new NullReferenceException("DaoFactory type can not be found.");

                Type DaoFactoryBaseType = Type.GetType("AndrewGolik.DaoTraining.DataAccessLayer.DaoFactory");
                if (!DaoFactoryBaseType.IsAssignableFrom(DaoFactoryType))
                    throw new ArgumentException("DaoFactory type does not inherits from AndrewGolik.DaoTraining.DataAccessLayer.DaoFactory.");


                DaoFactory daoFactory = (DaoFactory)Activator.CreateInstance(DaoFactoryType);
                return daoFactory;
            }
            
        }
         
       


    }
}