How to create a shopping cart?

[Shortie]

I am trying to create a shopping cart.
on the first page the user will select which items to buy, next page they will confirm all purchases and on the last page an invoice must be displayed

Im having alot of trouble with the first page. I dont know how to select the items in a gridview store and them into an array or session variable. I tried using doin this:

 Dim row As GridViewRow = grdProducts.SelectedRow

AddItem(i).ID = CInt(grdProducts.SelectedRow.Cells(0).Text)
AddItem(i).Name = grdProducts.SelectedRow.Cells(1).Text
AddItem(i).Code = grdProducts.SelectedRow.Cells(2).Text
AddItem(i).Price = CInt(grdProducts.SelectedRow.Cells(3).Text)

Session("AddedItem") = AddItem

Dim NewData As New TableCell
Dim NewRow As New TableRow

NewData.Text = CStr(AddItem(1).ID)
NewRow.Cells.Add(NewData)
NewData = New TableCell
NewData.Text = AddItem(1).Name
NewRow.Cells.Add(NewData)
NewData = New TableCell
NewData.Text = AddItem(1).Code
NewRow.Cells.Add(NewData)
NewData = New TableCell
NewData.Text = CStr(AddItem(1).Price)
NewRow.Cells.Add(NewData)

Table1.Rows.Add(NewRow)

but it still does not work