WingtipToys web response issues

Question

I'm completely stumped, looked over multiple forums and examples of which people had similar issues, but I cant seem to trace why I'm getiing this "System.Net.ProtocolViolationException: You must write ContentLength bytes to the request stream before calling [Begin]GetResponse." error. It happens on line 206 of my code: HttpWebResponse objResponse = (HttpWebResponse)objRequest.GetResponse();

if someone could please just point me in the right direction here...been trying to figure it out and its driving me nuts

thanks!

using System;
using System.Collections;
using System.Collections.Specialized;
using System.IO;
using System.Net;
using System.Text;
using System.Data;
using System.Configuration;
using System.Web;
using WingtipToys;
using WingtipToys.Models;
using System.Collections.Generic;
using System.Linq;

public class NVPAPICaller
{
//flag that determines the paypal environment (live or sandbox)
private const bool bSandbox = true;
private const string CVV2 = "CVV2";

//Live strings.
private string pEndPointURL = "http://api-3t.sandbox.paypal.com/nvp";
private string host = "www.paypal.com";

//sandbox strings.
private string pEndPointURL_SB = "http://api-3t.sandbox.paypal.com/nvp";
private string host_SB = "www.sandbox.paypal.com";

private const string SIGNATURE = "SIGNATURE";
private const string PWD = "PWD";
private const string ACCT = "ACCT";
//replace <Your API username> with your api username
//replace api pass with pass
//repalce sig with sig
public string APIUsername = "deleted";
private string APIPassword = "deleted";
private string APISignature = "deleted";
private string Subject = "";
private string BNCode = "PP-ECWizard";

//HttpWebRequest Timeout Specified in milliseconds
private const int Timeout = 15000000;
private static readonly string[] SECURED_NVPS = new string[] { ACCT, CVV2, SIGNATURE, PWD };

public void SetCredentials(string Userid, string Pwd, string Signature)
{
    APIUsername = Userid;
    APIPassword = Pwd;
    APISignature = Signature;
}

public bool ShortcutExpressCheckout(string amt, ref string token, ref string retMsg)
{
    if(bSandbox)
    {
        pEndPointURL = pEndPointURL_SB;
        host = host_SB;
    }

    string returnURL = "http://localhost:17394/Checkout/CheckoutReview.aspx";
    string cancelURL = "http://localhost:17394/Checkout/CheckoutCancel.aspx";

    NVPCodec encoder = new NVPCodec();
    encoder["METHOD"] = "SetExpressCheckout";
    encoder["RETURNURL"] = returnURL;
    encoder["CANCELURL"] = cancelURL;
    encoder["BRANDNAME"] = "Wingtip Toys Sampe Application";
    encoder["PAYMENTREQUEST_0_AMT"] = amt;
    encoder["PAYMENTREQUEST_0_ITEMAMT"] = amt;
    encoder["PAYMENTREQUEST_0_PAYMENTACTION"] = "Sale";
    encoder["PAYMENTREQUEST_0_CURRENCYCODE"] = "USD";

    //get the shopping cart products

    using (WingtipToys.Logic.ShoppingCartActions myCartOrders = new WingtipToys.Logic.ShoppingCartActions())
    {
        List<CartItem> myOrderList = myCartOrders.GetCartItems();

        for (int i = 0; i < myOrderList.Count; i++)
        {
            encoder["L_PAYMENTREQUEST_0_NAME" + i] = myOrderList[i].Product.ProductName.ToString();
            encoder["L_PAYMENTREQUEST_0_AMT" + i] = myOrderList[i].Product.UnitPrice.ToString();
            encoder["L_PAYMENTREQUEST_0_QTY" + i] = myOrderList[i].Quantity.ToString();
        }
    }


    string pStrrequestforNvp = encoder.Encode();
    string pStresponsenvp = HttpCall(pStrrequestforNvp);

    NVPCodec decoder = new NVPCodec();
    decoder.Decode(pStresponsenvp);

    string strAck = decoder["ACK"].ToLower();
    if (strAck != null && (strAck == "success" || strAck == "successwithwarning"))
    {
       // token = decoder["TOKEN"];
       // string ECURL = "http://" + host + "/cgi-bin/webscr?cmd=_express-checkout" + "&token=" + token;
       // retMsg = ECURL;
        return true;
    }
    else
    {
        retMsg = "ErrorCode=" + decoder["L_ERRORCODE0"] + "&" + "Desc=" + decoder["L_SHORTMESSAGE0"] + "&" +
            "Desc2=" + decoder["L_LONGMESSAGE0"];
        return false;
    }
}

public bool GetCheckoutDetails(string token, ref string PayerID, ref NVPCodec decoder, ref string retMsg)
{
    if (bSandbox)
    {
        pEndPointURL = pEndPointURL_SB;
    }

    NVPCodec encoder = new NVPCodec();
    encoder["METHOD"] = "GetExpressCheckoutDetails";
    encoder["TOKEN"] = token;


    string pStrrequestforNvp = encoder.Encode();
    string pStresponsenvp = HttpCall(pStrrequestforNvp);

    decoder = new NVPCodec();
    decoder.Decode(pStresponsenvp);

    string strAck = decoder["ACK"].ToLower();
    if (strAck != null & (strAck == "success" || strAck == "successwithwarning"))
    {
        PayerID = decoder["PAYERID"];
        return true;
    }
    else
    {
        retMsg = "ErrorCode=" + decoder["L_ERRORCODE0"] + "&" + "Desc=" + decoder["L_SHORTMESSAGE0"] + "&" + "Desc2=" + decoder["L_LONGMESSAGE0"];
        return false;
    }
}

public bool DoCheckoutPayment(string finalPaymentAmount, string token, string PayerID, ref NVPCodec decoder, ref string retMsg)
{
    if (bSandbox)
    {
        pEndPointURL = pEndPointURL_SB;
    }

    NVPCodec encoder = new NVPCodec();
    encoder["METHOD"] = "DoExpressCheckoutPayment";
    encoder["TOKEN"] = token;
    encoder["PAYERID"] = PayerID;
    encoder["PAYMENTREQUEST_0_AMT"] = finalPaymentAmount;
    encoder["PAYMENTREQUEST_0_CURRENCYCODE"] = "USB";
    encoder["[AYMENTREQUEST_0_PAYMENTACTION"] = "Sale";

    string pStrrequestforNvp = encoder.Encode();
    string pStresponsenvp = HttpCall(pStrrequestforNvp);

    decoder = new NVPCodec();
    decoder.Decode(pStresponsenvp);

    string strAck = decoder["ACK"].ToLower();
    if(strAck != null && (strAck == "success" || strAck == "successwithwarning"))
    {
        return true;
    }
    else
    {
        retMsg = "ErrorCode=" + decoder["L_ERRORCODE0"] + "&" + "Desc=" + decoder["L_SHORTMESSAGE0"];

        return false;
    }
}

public string HttpCall(string NvpRequest)
{
    string url = pEndPointURL;

    string strPost = NvpRequest + "&" + buildCredentialsNVPString();
    strPost = strPost + "&BUTTONSOURCE=" + HttpUtility.UrlEncode( BNCode );
   // ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls11;    //Thank you stack overflow

    HttpWebRequest objRequest = (HttpWebRequest)WebRequest.Create(url);
    objRequest.Timeout = Timeout;
    objRequest.Method = "POST";
    objRequest.ContentLength = strPost.Length;




    try
    {
        using (StreamWriter myWriter = new StreamWriter(objRequest.GetRequestStream()))
        {
            myWriter.Write(strPost);
        }
    }
    catch (Exception)
    {
        //No logging for this tutorial
    }

    try
    {
        //Retrieve the Response returned from the NVP API call to PayPal.
        HttpWebResponse objResponse = (HttpWebResponse)objRequest.GetResponse();

        string result;

        using (StreamReader sr = new StreamReader(objResponse.GetResponseStream()))
        {
            result = sr.ReadToEnd();
        }

        return result;
    }
    catch (WebException ex)
    {
        using (var stream = ex.Response.GetResponseStream())
        using (var reader = new StreamReader(stream))
        {
            Console.WriteLine(reader.ReadToEnd());
        }
    }

Answer 1

You are doing few things wrong. You shuold convert the request text to bytearray and pass that to stream for writing and then call GetResponse() like

var arr = System.Text.Encoding.UTF8.GetBytes(strPost);

objRequest.ContentLength = arr.Length;

    try
    {
        using (StreamWriter myWriter = new StreamWriter(objRequest.GetRequestStream()))
        {
            myWriter.Write(arr, 0, arr.Length);
        }
    }