New to Three Tier Architecture using class library.

Hi,

I am working on my first project using the Three Tier Architecture. I am following the article "Creating a Business Logic Layer" but I want to use a class library to separate the presentation layer from the DAL/BLL

I am having a problem with the BLL when I try to use it I get the error "System.NullReferenceException: Object reference not set to an instance of an object."

In my solution I have my website where there is all the presentation tier, then I have a class library that contains the BLL and a Dataset DAL

If I do not use the BLL everything works properly

        Dim topnavbll As New ClassLibrary.TestDSTableAdapters.Tets_TopNavigationTableAdapter
        GridView1.DataSource = topnavbll.GetTopNavigation()
        GridView1.DataBind()


but when I try to use the BLL I get t ...