ASP.NET Session Shopping Cart Items issue on pageload not updating

I.e. I have a piece of code on my page as follows, which is in page_load

Dim subTotal As Integer = 0
    For Each item As CartItem In ShoppingCart.Instance.Items
        subTotal += 1
    Next

    strShoppingCart.Append(subTotal).Append(" Items")
    shoppingCartItems.Text = strShoppingCart.ToString()

And I can then add items to my cart as follows

Protected Sub Update_Click(ByVal sender As Object, ByVal e As EventArgs) Dim rowscount As Integer = productListTable.Rows.Count

    For Each row As GridViewRow In productListTable.Rows
        If row.RowType = DataControlRowType.DataRow Then
            ' We'll use a try cat开发者_开发技巧ch block in case something other than a number is typed in. If so, we'll just ignore it.
            Try
                ' Get the productId from the GridView's datakeys
                Dim productId = Convert.ToInt32(productListTable.DataKeys(row.RowIndex).Value)
                ' Find the quantity TextBox and retrieve the value
                Dim quantity = Integer.Parse(CType(row.Cells(1).FindControl("txtQuantity"), TextBox).Text)
                'Dim price = Decimal.Parse(CType(row.Cells(1).FindControl("TradePriceField"), Label).Text)
                Dim price = Decimal.Parse("16.00")
                Dim productName = CType(row.Cells(1).FindControl("ProductNameField"), Label).Text
                Dim packSize = Integer.Parse(CType(row.Cells(1).FindControl("PackSizeField"), Label).Text)
                Dim stockIndicator = Integer.Parse(CType(row.Cells(1).FindControl("PackSizeField"), Label).Text)
                ShoppingCart.Instance.AddItem(productId, quantity, price, productName, packSize, stockIndicator)


            Catch ex As FormatException

            End Try
        End If
    Next
End Sub

The problem is as follows

Page Load Items Count is 0

I add a product the page still says 0 Items when there is actually 1 item in session I refresh the page the counter goes to one

How can I to read from correct session count ?

Page_Load is going to fire before Update_Click, which is why you're not seeing the count increase after the initial form submit. You'll need to either update the shoppingCartItems control after Update_Click executes, or you can Response.Redirect back to the page to get the display to update. I personally like to use Response.Redirect after a post because if the user refreshes the page then you won't see that browser message that says it is going to repost the data.

You also might want to check out the ASP.NET Page Life Cycle.

I had a similar problem with a shopping cart, but I used AJAX updatepanels and the Redirect did not work the AJAX way.

I used mycartlistview.DataBind() in my code after an item was added to the shopping cart.