shopping cart problem

Edited by SomeNewKid. Please post code between<code> and</code> tags.

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Hi all…

I'm having this shopping cart problem…what I'm trying to do here, is that when a user click the Add To Cart button in the lunch_cart.aspx to add his desired lunch menu to his shopping cart in cafe_cart.aspx, the dish should be added into the shopping cart right? Let's say he adds Dish A, then he can see his Dish A in the shopping cart. But, he can't see the Quantity, Sub Total and Total in the cart! Moreover, let's say when he chooses to add another Dish B to the cart, the cart instead replaced the Dish A which had been added earlier! The only thing that my shopping cart can read/detect is the Dish ID, Dish Name and Price Per Set that are displayed correctly. Here's the relevant code for the lunch_cart.aspx:

Sub Page_Load(sender As Object, e As EventArgs)
 Dim dt As DataTable
 Dim nr As DataRow
 Dim i As Integer
 Dim strConn As String = "PROVIDER=Microsoft.Jet.OLEDB.4.0;DATA SOURCE=" & server.mappath("EzySys.mdb") & ";"
 Dim Conn As New OLEDBConnection(strConn)
 Dim strSQL As String = "SELECT * FROM dish_info WHERE Dish_ID='" & Request.Item("dishid") & "'"
 Conn.Open()
 Dim Cmd As New OLEDBCommand(strSQL,Conn)
 Dim Dr As OLEDBDataReader=Cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection)
 if DR.read()
 lbllunchdesc1.Text = DR("Dish_Desc").ToString()
 lbllunchp1.Text = CStr(FormatCurrency(DR("Dish_Price").ToString()))
 lbllunchp1.Text = RIGHT(lbllunchp1.Text,Len(lbllunchp1.Text)-1)
 img1.imageurl = DR("Dish_Photo").ToString()
 lblgrocery.text = DR("Dish_Name").ToString()
 lblDishID.text = DR("Dish_ID").ToString()
 end if
 End Sub
Sub AddToCart(sender As Object, e As EventArgs)
 If txtQty.text="" Then
 lblErrorMsg.text="Please enter a valid number!"
 Else If NOT IsNumeric(txtQty.text) Then
 lblErrorMsg.text="Please enter a valid number!"
 Else If CInt(txtQty.text)<=0 OR CInt(txtQty.text)>10 Then
 lblErrorMsg.text="Please enter a vaild number!"
 Else If IsNumeric(txtQty.text) Then
 Dim conn As OleDbConnection
 Dim strSelect As String
conn = New OleDbConnection("PROVIDER=Microsoft.Jet.OLEDB.4.0; " & _
 "Ole DB Services=-4; Data Source= " & server.mappath("EzySys.mdb"))
 strSelect = "SELECT * FROM dish_info WHERE Dish_ID='" & Request.Item("dishid") & "'"
 conn.Open()
 Dim Cmd As New OLEDBCommand(strSelect ,conn)
 Cmd.ExecuteNonQuery()
 conn.Close()
 Response.Redirect("cafe_cart.aspx?dishid=" & Request.Item("dishid"))
 End If
End Sub
And here's the relevant code for cafe_cart.aspx:
 Dim objDT As System.Data.DataTable
 Dim objDR As System.Data.DataRow
 Sub Page_Load(sender As Object, e As EventArgs)
 'If Not Page.IsPostBack Then
 makeCart()
 'End If
 End Sub
 Function makeCart()
 Dim objDT As System.Data.DataTable
 Dim objDR As System.Data.DataRow
 objDT = New System.Data.DataTable("CafeCart")
 objDT.Columns.Add("Dish ID", GetType(String))
 objDT.Columns.Add("Dish Name", GetType(String))
 objDT.Columns.Add("Price Per Set", GetType(Decimal))
 objDT.Columns.Add("Quantity", GetType(Decimal))
 objDT.Columns.Add("Sub Total", GetType(Decimal))
 Session("CafeCart") = objDT
 Call AddDishes()
 End Function
 Function AddDishes()
 Dim strConn As String = "PROVIDER=Microsoft.Jet.OLEDB.4.0;DATA SOURCE=" & server.mappath("EzySys.mdb") & ";"
 Dim Conn As New OLEDBConnection(strConn)
 Dim strSQL As String = "SELECT * FROM dish_info WHERE Dish_ID='" & Request.Item("dishid") & "'"
 Conn.Open()
 Dim Cmd As New OLEDBCommand(strSQL,Conn)
 Dim Dr As OLEDBDataReader=Cmd.ExecuteReader(System.Data.CommandBehavior.CloseConnection)
 Dim objDT As System.Data.DataTable
 Dim objDR As System.Data.DataRow
 objDT = Session("CafeCart")
 Dim DishID As String
 Dim DishName As String
 Dim DishPrice As String
 Dim DishQty As String
 Dim DishSubT As String
 If Dr.Read()
 DishID = Dr("Dish_ID").ToString()
 DishName = Dr("Dish_Name").ToString()
 DishPrice = CStr(FormatCurrency(Dr("Dish_Price").ToString()))
 DishPrice = RIGHT(DishPrice,Len(DishPrice)-1)
 End If
 DishQty = CDbl(Request.Item("txtQty"))
 Dim qty As Double, price As Double
 qty = CDbl(Request.Item("txtQty"))
 price = CDbl(DishPrice)
 DishSubT = CDbl(qty * price)
 Conn.Close()
 'this code is suppose to check whether a user has added the same item or not
 'if he has added the same item again, then only the qty needs to be updated
 Dim blnMatch As Boolean = False
 For Each objDR In objDT.Rows
 If objDR("Dish Name") = DishName Then
 objDR("Quantity") += DishQty
 blnMatch = True
 Exit For
 End If
 Next
 'if the user has not added a new dish before, then a new row can be added
 If Not blnMatch Then
 objDR = objDT.NewRow
 objDR("Dish ID") = DishID
 objDR("Dish Name") = DishName
 objDR("Price Per Set") = DishPrice
 objDR("Quantity") = DishQty
 objDR("Sub Total") = DishSubT
 objDT.Rows.Add(objDR)
 End If
 Session("CafeCart") = objDT
 dgCafe.DataSource = objDT
 dgCafe.DataBind()
 End Function
 'this function is to calculate the subtotal (or is it grandtotal?)
 Function GetItemTotal() As Decimal
 Dim intCounter As Integer
 Dim decRunningTotal As Decimal
 For intCounter = 0 To objDT.Rows.Count - 1
 objDR = objDT.Rows(intCounter)
 decRunningTotal += (objDR("Price Per Set") * objDR("Quantity"))
 Next
 Return decRunningTotal
 End Function
 'this code allows user to remove the dish from shopping cart
 Sub Delete_Item(s As Object, e As DataGridCommandEventArgs)
 objDT = Session("CafeCart")
 objDT.Rows(e.Item.ItemIndex).Delete()
 Session("CafeCart") = objDT
 dgCafe.DataSource = objDT
 dgCafe.DataBind()
 lblTotal.Text = "RM" & GetItemTotal() 'recalculate the total after removing dish
 End Sub

erm...i still can't solve the problem...the same thing happened when i modified a little. anyone can help me get on with this? i've been stuck with this coding for more than a month!
took a brief look at ur code, hasn't gone the full length. Well, for starter, u need to encode ur lunch quantity in ur url when u redirects to the cart.aspx....like -- Response.Redirect("cafe_cart.aspx?dishid=" & Request.Item("dishid") & "txtQty=" & txtQty.text) --
hi tantian

thanks a lot for your suggestion. i've tried your method and yes, it worked! but still... other problem persists...anyway, i'll try to modify and code again for a few more days. hopefully, i can solve the problem that's been bugging me for almost two months! ouch...
Suggestion: In your code, I see that your doing validation of the textboxes via if..else statements. I recommend to look at the validator controls. They are easy to use and you surely will benefit from them.