Having Trouble Following Tutorial - Working With Data In ASP.NET 2.0 :: Creating A Data Access Layer

Hi

I'm having problems following the tutorial on creating a data access layer -  http://www.asp.net/learn/dataaccess/tutorial01cs.aspx?tabid=63 - when I try to compile in Visual Studio 2005 I get namespace could not be found.

I followed exactly the tutorial - I created a dataset and added this code in my aspx page. 
 <asp:GridView ID="GridView1" runat="server"
             CssClass="DataWebControlStyle">
               <HeaderStyle CssClass="HeaderStyle" />
               <AlternatingRowStyle CssClass="AlternatingRowStyle" />
In my C# file I added these lines...

    using NorthwindTableAdapters; <<<<<this is the problem - where does this come from?

   protected void Page_Load(object sender, EventArgs e)
    {
        ProductsTableAdapter productsAdapter = new
         ProductsTableAdapter();
        GridView1.DataSource = productsAdapter.GetProducts();
        GridView1.DataBind();
    }

Thanks in advance