Get Paypal Express cart Price right before checkout - asp.net

Question

I am using paypal express checkout and I'm trying to get the total value that is in the shopping cart when the user decides to checkout. My shipping rate is going to be based on the total price and although I have the shipping calculations filled out in my paypal account settings, the shipping cost is not showing up in the checkout screen. How would I grab the total shopping cart price right upon checkout so that I can add the shipping cost? What I have so far is only the values after the user has checked out and they are returned back to my website but at this point it is too late to add shipping.
Dim authToken As String = "sdf5414FdsfDFS5eEF52s336DFLLJUhhbuzek64"
Dim txToken As String = Request.QueryString("tx")
txToken = "4GGSES84eEWSS"
Dim strRequest As String = "cmd=_notify-synch&tx=" & txToken & "&at=" & authToken
'Dim Payerinfo As New PayerInfo
'Dim trans As New Transaction
'Dim tra As New PayPal.PayPalAPIInterfaceService.Model.GetTransactionDetailsReq
'post back to either sandbox or live
Dim strSandbox As String = "https://www.sandbox.paypal.com/cgi-bin/webscr"
Dim strLive As String = "https://www.paypal.com/cgi-bin/webscr"
Dim req As HttpWebRequest = CType(WebRequest.Create(strSandbox), HttpWebRequest)
'req.Headers = valHeader
'Set values for the request back
req.Method = "POST"
req.ContentType = "application/x-www-form-urlencoded"
req.ContentLength = strRequest.Length
'Send the request to PayPal and get the response
Dim streamOut As StreamWriter = New StreamWriter(req.GetRequestStream(), Encoding.ASCII)
streamOut.Write(strRequest)
streamOut.Close()
Dim streamIn As StreamReader = New StreamReader(req.GetResponse().GetResponseStream())
Dim strResponse As String = streamIn.ReadToEnd()
streamIn.Close()
If Not String.IsNullOrEmpty(strResponse) Then
Dim results As New Dictionary(Of String, String)
Dim reader As New StringReader(strResponse)
Dim line As String = reader.ReadLine()
If line = "SUCCESS" Then
'FormView1.Visible = False
While True
Dim aLine As String
aLine = reader.ReadLine
If aLine IsNot Nothing Then
Dim strArr() As String
strArr = aLine.Split("=")
results.Add(strArr(0), strArr(1))
Else
Exit While
End If
End While
' Displays all the keys for results, helps to see what the keys are named for writing to text file
For Each kvp As KeyValuePair(Of String, String) In results
Dim v1 As String = kvp.Key
Dim v2 As String = kvp.Value
Response.Write(v1.ToString _
+ ": " + v2 + "<br /> ")
Next
End If
I have also been trying to declare a session variable and add to it every time the add to cart button is clicked but I see a problem in this because I don't know how long the items will stay in the paypal cart and if the session variable session runs out of time and is cleared, they will then receive free shipping since the shipping amount clears out. Is their any way to make this work?
Protected Sub AddToCartBtn_Click(sender As Object, e As EventArgs)
Session("CartAmount")
Dim itemNumber As String = str2
Dim itemAmount As String = price
Dim currencyCode As String = "USD"
Dim addItem As Integer = 1
Dim ppHref As StringBuilder = New StringBuilder()
ppHref.Append("https://www.sandbox.paypal.com/cgi-bin/webscr?cmd=_cart")
ppHref.Append("&business=" + business)
ppHref.Append("&item_name=" + itemName)
ppHref.Append("&item_number=" + itemNumber)
ppHref.Append("&amount=" + itemAmount)
ppHref.Append("&currency_code=" + currencyCode)
Session("CartAmount") = (cartTotal + Session("CartAmount"))
End Sub

Answer 1

You can pass shopping cart values in the provided variable from the following url reference,
https://developer.paypal.com/docs/classic/paypal-payments-standard/integration-guide/Appx_websitestandard_htmlvariables/#id08A6HF080O3