Incrementing a variable in VB.net with a button - asp.net

Question

I'm trying to increment my variable on a button click. It increments only once. It seems as though it's getting lost when it reloads the page.
I'm using the following code:
Dim ItemSelect As New ArrayList()
Dim Quantities As New ArrayList()
Dim itemQtyOrdered As Integer
Public Sub ShtickDataList_ItemCommand(ByVal source As Object, ByVal e As System.Web.UI.WebControls.ListViewCommandEventArgs) Handles ShtickDataList.ItemCommand
If e.CommandName = "ViewCart" Then
Response.Redirect("~/ShoppingCart.aspx")
End If
If e.CommandName = "addToCart" Then
Dim itemQuantity As DropDownList = e.Item.FindControl("QuantityDropDown")
itemQtyOrdered = itemQuantity.SelectedValue
ItemSelect.Add(e.CommandArgument)
Quantities.Add(itemQtyOrdered)
Session("itemInCart") = ItemSelect
Session("quantities") = Quantities
viewInvoice()
End If
End Sub
Protected Sub viewInvoice()
Dim itemSelected As ArrayList = DirectCast(Session("itemInCart"), ArrayList)
Dim QuantityofItem As ArrayList = DirectCast(Session("quantities"), ArrayList)
Dim conn As SqlConnection
Dim comm As SqlCommand
Dim reader As SqlDataReader
Dim purimConnection2 As String = ConfigurationManager.ConnectionStrings("Purim").ConnectionString
conn = New SqlConnection(purimConnection2)
comm = New SqlCommand("SELECT ProductName FROM Products WHERE ProductID = #ProductID", conn)
Dim i As Integer
For i = 0 To ItemSelect.Count - 1
comm.Parameters.Add("#ProductID", Data.SqlDbType.Int)
comm.Parameters("#ProductID").Value = ItemSelect(i)
Next
Try
conn.Open()
reader = comm.ExecuteReader()
ViewCartlink.Text = "View Cart: (" & ItemSelect.Count & ")"
Finally
conn.Close()
End Try
End Sub

Answer 1

Ah, you may be referring to ItemSelect and Quantities lists. You need to look for them in Session and only create them if they are not in the Session. I am rusty on VB.NET, so this is C# version. In Page_Load:
ItemSelect = (ArrayList)Session["itemInCart"];
if (ItemSelect == null)
{
ItemSelect = new ArrayList();
Session["itemInCart"] = ItemSelect;
}
and the same for Quantities.
Also, your loop in viewInvoice method is wrong. For more than one item in ItemSelect list you are adding multiple parameters with the same name. You probably only wanted to do it once with
comm.Parameters("#ProductID").Value = ItemSelect(ItemSelect.Count - 1)