Please I am trying to understand the arraylist.

Please anyone help; why I am getting this message "Object reference not set
to an instance of an object" when line no (13) get executed in the following
code:

1-   ' Create a new ArrayList to hold the Customer objects.
2-   Dim customerArray As New ArrayList()

3-  'Add customers to the ArrayList of Customer objects.
4-   Dim x As Integer
5-   For x = 0 To 999
6-      customerArray.Add(New Customer("Customer" + x.ToString()))
7-  Next x

8-  ' Add orders to each Customer object in the ArrayList.
9-   Dim customer1 As Customer
10-   For Each customer1 In customerArray
11-         Dim y As Integer
12-        For y = 0 To 14
13-              customer1.CustomerOrders.Add(New Order("Order" +
y.ToString()))
14-        Next y

-----------Customer & Order Classes-----
Public Class Customer
   Private _CustomerOrders As ArrayList
   Private _Name As String
   Public Property Name() As String
       Get
           Return _Name
       End Get
       Set(ByVal value As String)
           _Name = value
       End Set
   End Property
   Public Property CustomerOrders() As ArrayList
       Get
           Return _CustomerOrders
       End Get
       Set(ByVal value As ArrayList)
           _CustomerOrders = value
       End Set
   End Property
   Public Sub New(ByVal Name As String)
       _Name = Name
   End Sub
End Class
---------------
Public Class Order
   Private _Name As String
   Public Property Name() As String
       Get
           Return _Name
       End Get
       Set(ByVal value As String)
           _Name = value
       End Set
   End Property
   Public Sub New(ByVal Name As String)
       _Name = Name
   End Sub
End Class
------------------

Thank you