Extension Method in C# 2.0

What namespace do I need to get my extension to work

Here is my Extension Method

using System;
using System.Collections.Generic;
using System.Web;
using System.Data;

namespace MyUtilities
{
    public static class DataReaderExtensions
    {
        public static DataTable ToDataTable(IDataReader reader)
        {
            DataTable table = new DataTable();
            table.Load(reader);
            return table;
        }
    }
}

When I try to use it in like this

Session["Master"] = cust.GetCustomerOrderSummary((string)Session["CustomerNumber"]).ToDataTable();

it doesn't work. This is .net 2.0