Shopping Cart Query

rsm42 · April 9th, 2007, 08:40 AM

Hi,

I'm finalising an e-commerce based web site written in asp.net 1.1. using vb.net. Whilst testing the functionality I've noted that if a customer adds the same item twice, the shopping cart (which is a datagrid) displays both items as separate rows within the datagrid.

To improve this I would like to put an if statement in to say if the productID is the same, increase the quantity by one. From a coding perspective can you advise how I would exactly do this ? I've included some sample code from the "Add To Cart" sub procedure for reference :

Code:

 Sub AddToCart(sender As Object, e As EventArgs)

        'Define CartID
        Dim CartID As Double

        'Passes ProductID as sender
        Dim intProductID As Integer = sender.CommandArgument'<%# DataBinder.Eval(Container.DataItem, "intProductID")%>'

        'Set quantity value
        Dim Quantity As Integer
        Quantity = 1

        'Define intQuantityInStock and reference to CheckQuantity function
        Dim intQuantityInStock As Integer = CheckQuantity(intProductID)

        'Check enough quantity in stock before adding to cart

        'Label used for testing purposes
        lblQuantity.Text = quantity
        lblQuantity.Visible = False

        'If value intQuantityInStock is less than quantity value
        If intQuantityInStock < quantity
            'Display low in stock error message
            lblError.Text = "This item is currently low in stock. Please select an alternative</b>"
            lblError.Visible = True
        End If


        'Set date and time
        Dim dtNow as Date = Date.Now
        Dim ts as String
        ts = dtNow.ToString("dd/MM/yyyy"  & " " & "HH:mm:ss")

        'Updates CartItems table in db
        UpdatetblCartItems(Session("CartID"),Quantity,intProductID,ts)

        'Goto shopping cart page
         Response.Redirect("cart.aspx")
     End Sub

Any online examples would help - thanks.

dparsons · April 9th, 2007, 08:48 AM

I assume this method is the one you are going to want to look at

UpdatetblCartItems(Session("CartID"),Quantity,intP roductID,ts)

It is here, again I assume, that you are writing values to a database which in turn is bound to the datagrid, am I correct?

If so, it seems that when that method is called, you simply fire a SQL INSERT statement (or stored procedure) that adds the item information to the table. To solve your problem, you could approach it 2 different ways, IMHO, and they are as follows:

1)You could run a SELECT count([value]) from shoppingcart where pID = [productID to add] then ExecuteScalar() to return the value. If the value returned is 0 you know that you then need to insert a new row but if n > 0 then you know that you need to call an update statement.

2)You could write a stored procedure that handled this logic for you and the decision to update or insert would be made in SQL Server and not in your code.

Personally, I would use the second option because it cuts out an additional round trip to SQL while still providing the same functionality. hth.

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rsm42 · April 9th, 2007, 09:36 AM

Thanks - would the second option still be relevant for an access database, as is the case here ?

dparsons · April 9th, 2007, 09:48 AM

I haven't used access in quite a few years, but I do know that you can't use stored procedures inside of Access. However, I am not sure if you could achieve the same effect by writing and saving a query inside of access and calling that query from your code.

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Read this if you want to know how to get a correct reply for your question:
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^^Took that from planoie's profile^^
^^Modified text taken from gbianchi profile^^
================================================== =========
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rsm42 · April 10th, 2007, 01:32 PM

ok - thanks for the advice