Problem with class file

[miss nadia]

i got problems with my class file. most of the errors saying that 'Object reference not set to an instance of an object'. it looks like all functions in class file cannot be performed, even i do declare the class at code-behind file. do i have to call the class file in .aspx page? like this <%# Imports ... %>. this is page for CheckOut.aspx.vb.

Partial Class Checkout_CheckOut
Inherits System.Web.UI.Page

Private order As Order
Private cust As Customer
Private cart As ShoppingCart

Protected Sub Page\_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    cart = Session("cart")

    If Session("order") Is Nothing Then
        order = New Order(DateTime.Now, Nothing, Session("cart"))
        Session("order") = order
    Else
        order = Session("order")
        cart = order.Cart
    End If

    cust = New Customer(txtEmail.Text, txtLastName.Text, txtFirstName.Text, \_
        txtAddress.Text, txtCity.Text, txtState.Text, txtPostCode.Text, txtPhone.Text, \_
        txtEmail.Text)
    order.Cust = cust

    lblSubtotal.Text = order.SubTotal.ToString("c")
    lblShipping.Text = order.Shipping.ToString("c")
    lblTotal.Text = order.Total.ToString("c")
End Sub

Protected Sub Wizard1\_FinishButtonClick(ByVal sender As Object, ByVal e As  \_
    System.Web.UI.WebControls.WizardNavigationEventArgs) Handles Wizard1.FinishButtonClick

    ' process credit card information here
    Dim success As Boolean
    success = OrderDB.WriteOrder(order)      'the function WriteOrder from OrderDB class 
    Session("cart") = Nothing                'can't be performed
    Session("order") = Nothing
    If success Then
        Response.Redirect("Confirmation.aspx")
    Else
        Response.Redirect("Confirmation.aspx?Error=1")
    End If
End Sub

End Class

[doWhileSomething]

I can't make sense from the logic, nor do I know what your class objects look like. But, in the page load event, it appears that not all objects have the chance of being instantiated. Customer - this is always created Order - creates a new object unless found in the session object. Cart - Never creates a new instance and assumes there will always be a "cart" object in session object. The easiest way is to put a break point on your code and see where it blows up.. :wtf:

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