Problems in my WebRequest/WebResponse

Question

So I was struggling with making head or tail out of the PayPal documentation and always felt that something was not right with my Webrequest. So I stripped all the code back to basic and simply submitted the request via HTTP and the PLUS side is that I now get a response back from the PayPal sandbox server where

ACK=Success and TOKEN=Valid-token-value-here

there are some other variables returned too, such as CORRELATIONID and TIMESTAMP.

And hence so I tried some of the webrequest samples and I simply get a blank screen instead of being redirected to Paypal for the (sandbox) customer to complete payment. So if anyone can post their WebRequest method that would be great. Here is the code I used for my webrequest, I'm sure its wrong but cannot pinpoint where it is going wrong.

Thank you

'------------------------------------------------------------------------
'-> [Function] SetExpressCheckout    
'------------------------------------------------------------------------
Function SetExpressCheckout(ByRef pRtnReturnUrl As String) As Boolean
  '
  Dim _sxForwarding As String = Nothing
  Dim _sxNameValCol As System.Collections.Specialized.NameValueCollection = Nothing
  Dim _sxCounter As Integer = Nothing
  '
  '-> Init
  _sxForwarding = ""
  SetExpressCheckout = False
  _pgHost = "https://api-3t.sandbox.paypal.com/nvp"
  '-> Key/Value Collection Params
  _sxNameValCol = New System.Collections.Specialized.NameValueCollection()
  _sxNameValCol.Add("METHOD", "SetExpressCheckout")
  _sxNameValCol.Add("USER", "username-email-address-here")
  _sxNameValCol.Add("PWD", "password-here")
  _sxNameValCol.Add("SIGNATURE", "signature-here")
  _sxNameValCol.Add("PAYMENTREQUEST_0_AMT", _pgBasket.BasketTotalIncDelivery / 100)
  _sxNameValCol.Add("BUTTONSOURCE", "PP-ECWizard")
  _sxNameValCol.Add("RETURNURL", _pgReturnURL)
  _sxNameValCol.Add("CANCELURL", _pgCancelURL)
  _sxNameValCol.Add("REQCONFIRMSHIPPING", "0")
  _sxNameValCol.Add("NOSHIPPING", "2")
  _sxNameValCol.Add("LOCALECODE", "EN")
  _sxNameValCol.Add("PAYMENTREQUEST_0_PAYMENTACTION", "Sale")
  _sxNameValCol.Add("PAYMENTREQUEST_0_CURRENCYCODE", "GBP")
  _sxNameValCol.Add("PAYMENTREQUEST_0_SELLERPAYPALACCOUNTID", "seller-email-here")
  _sxNameValCol.Add("VERSION", "93.0")
  '-> UrlEncode
  For _sxCounter = 0 To _sxNameValCol.Count - 1
    If _sxCounter = 0 Then
      _sxForwarding = _sxForwarding & "?" & _sxNameValCol.Keys(_sxCounter) & "=" & Server.UrlEncode(_sxNameValCol(_sxCounter))
    Else
      _sxForwarding = _sxForwarding & "&" & _sxNameValCol.Keys(_sxCounter) & "=" & Server.UrlEncode(_sxNameValCol(_sxCounter))
    End If
  Next
  ' SUBMITTING ABOVE QUERYSTRING GENERATES VALID RESPONSE FROM PAYPAL 
  ' USING THE LINE BELOW
  'Response.Redirect(_pgHost & _sxForwarding)
   'SetExpressCheckout = True
  '======================================================================
  ' MY WEBREQUEST EFFORT
  '======================================================================
  '-> Locals
  Dim objRequest As System.Net.WebRequest = DirectCast(System.Net.WebRequest.Create(_pgHost), System.Net.WebRequest)
  Dim MyByteArray As Byte() = Nothing
  Dim MyResult As String = Nothing
  '
  '-> WebRequest
  objRequest.Timeout = 6000
  objRequest.Method = "POST"
  MyByteArray = Encoding.UTF8.GetBytes(_sxForwarding)
  objRequest.ContentType = "application/x-www-form-urlencoded"
  objRequest.ContentLength = MyByteArray.Length
  Try
    Using MyWriter As New System.IO.StreamWriter(objRequest.GetRequestStream())
      MyWriter.Write(_sxForwarding)
    End Using
    Try
      '-> WebResponse
      MyResult = ""
      Dim objResponse As System.Net.HttpWebResponse = DirectCast(objRequest.GetResponse(), System.Net.HttpWebResponse)
      Using MyReader As New System.IO.StreamReader(objResponse.GetResponseStream())
        MyResult = MyReader.ReadToEnd()
      End Using
      SetExpressCheckout = True
      pRtnReturnUrl = MyResult
      objResponse = Nothing
    Catch ex As Exception
      '-> Error
      pRtnReturnUrl = MyResult '("APIError.Aspx?ErrorCode=" & pRtnReturnUrl("L_ERRORCODE0") & "&Desc=" & pRtnReturnUrl("L_SHORTMESSAGE0") & "&Desc2=" & pRtnReturnUrl("L_LONGMESSAGE0"))
      SetExpressCheckout = False
    End Try
  Catch e As Exception
    '-> Error
    pRtnReturnUrl = MyResult '("APIError.Aspx?ErrorCode=" & pRtnReturnUrl("L_ERRORCODE0") & "&Desc=" & pRtnReturnUrl("L_SHORTMESSAGE0") & "&Desc2=" & pRtnReturnUrl("L_LONGMESSAGE0"))
    SetExpressCheckout = False
  End Try
  objRequest = Nothing
  MyByteArray = Nothing
  MyResult = Nothing
'
End Function

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DocZaf

Answer 1

I think that PayPal has an API that you can use.

If I'm right, that would make this much easier. You might want to look into it.

***** EDIT *****

I was right, here it is.

---

Still lost in code, just at a little higher level.

:-)

Answer 2

There is a detailed example below if you want to use or compare with yours:

http://www.codeproject.com/Articles/19184/Use-of-the-PayPal-payment-system-in-ASP-NET

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Fouad Roumieh