For this topic I’ve trouble too much on internet but I could not found a single crucial article which explained all of the required part to integration PayPal payment gateway for naïve users. In this article I will explain thoroughly all the requirements and techniques for integrating PayPal in your web application step by step.

Basic requirement to Integration PayPal payment in Asp.Net application:

1.   Should have PayPal Sandbox account (URL: https://developer.paypal.com/ ) for developer testing code.

2.   Should have one buyer (Personal Account) and one seller account (Business Account) PayPal account.

3.  PayPal API token (Signature) key

4.  PayPal business account email id

5.       Integrate PayPal payment with Application

Now let’s start step by step work to integrate PayPal payment.

Create PayPal account on PayPal Sandbox: Basically, PayPal provides an environment to developer that how they can integrate PayPal payment in their website. So just open URL: https://developer.paypal.com/ and click on SignUp option.

Fill all the required information and click on button ‘Agree and Submit’,

Now first step has been completed and I am moving on second step (Create buyer and seller or personal and business account). After logged in PayPal payment panel, there is a preconfigured account option visible through which you can complete second step..   

Now check out these two account information by selecting Test Account option logged in panel.

Now you have been completed second step successfully. Now I’m moving on third step (Having a valid PayPal API Token Key).

Now select ‘API and Payment Card Credential’ option from PayPal home.

Here you’ve a valid email id too, so all of the necessary things are over related with PayPal Account and payment API. Now I’m moving on Integration step.

So just create your web application in which you’re going to integrate PayPal payment. Here I’m just creating an application which contains some product information such as Product description, product price, product name and user can purchase it, simply, by clicking on ‘BuyNow’ button.

Aspx Page Code:

<%@ Page Title="Home Page" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeFile="Default.aspx.cs" Inherits="_Default" %>
 
<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
    <div>
        <table width="700" align="center" cellpadding="0" cellspacing="0">
            <tr>
                <td height="60">
                    <b>Paypal Integration in ASP.NET</b>
                </td>
            </tr>
            <tr>
                <td height="40" align="center">
                    <asp:GridView ID="gvPayPal" runat="server" AutoGenerateColumns="False" OnRowCommand="gvPayPal_RowCommand"
                        BackColor="#DEBA84" BorderColor="#DEBA84" BorderStyle="None" BorderWidth="1px"
                        CellPadding="3" CellSpacing="2">
                        <RowStyle ForeColor="#8C4510" BackColor="#FFF7E7" />
                        <Columns>
                            <asp:TemplateField HeaderText="Product Name">
                                <ItemTemplate>
                                    <asp:Label ID="lblName" runat="server" Text='<%#Eval("prodName") %>'></asp:Label>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Product Description">
                                <ItemTemplate>
                                    <asp:Label ID="lblDescription" runat="server" Text='<%#Eval("prodDesc") %>'></asp:Label>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Product price">
                                <ItemTemplate>
                                    <asp:Label ID="lblProductPrice" runat="server" Text='<%#Eval("prodPrice") %>'></asp:Label>
                                </ItemTemplate>
                            </asp:TemplateField>
                            <asp:TemplateField HeaderText="Buy Now">
                                <ItemTemplate>
                                    <asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="~/images/buy.png"
                                       Width="64" Height="64" CommandName="buy" CommandArgument="<%# ((GridViewRow) Container).RowIndex %>" />
                                </ItemTemplate>
                            </asp:TemplateField>
                        </Columns>
                        <FooterStyle BackColor="#F7DFB5" ForeColor="#8C4510" />
                        <PagerStyle ForeColor="#8C4510" HorizontalAlign="Center" />
                        <SelectedRowStyle BackColor="#738A9C" Font-Bold="True" ForeColor="White" />
                        <HeaderStyle BackColor="#A55129" Font-Bold="True" ForeColor="White" />
                        <SortedAscendingCellStyle BackColor="#FFF1D4" />
                        <SortedAscendingHeaderStyle BackColor="#B95C30" />
                        <SortedDescendingCellStyle BackColor="#F1E5CE" />
                        <SortedDescendingHeaderStyle BackColor="#93451F" />
                    </asp:GridView>
                </td>
            </tr>
        </table>
        <!-- PayPal Logo -->
        <table border="0" cellpadding="10" cellspacing="0" align="center">
            <tr>
                <td align="center">
                </td>
            </tr>
            <tr>
                <td align="center">
                    <a style="cursor:pointer;" title="Paypal payment gateway center" onclick="javascript:window.open('https://www.paypal.com/cgi-bin/webscr?cmd=xpt/Marketing/popup/OLCWhatIsPayPal-outside','olcwhatispaypal','toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=yes, resizable=yes, width=400, height=350');">
                        <img src="https://www.paypal.com/en_US/i/bnr/horizontal_solution_PPeCheck.gif" border="0"
                            alt="Solution Graphics"></a>
                </td>
            </tr>
        </table>
        <!-- PayPal Logo -->
    </div>
</asp:Content>

CS Page Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Configuration;
using System.Data.SqlClient;
using System.Data;
 
public partial class _Default : System.Web.UI.Page
{
    SqlConnection Con = new SqlConnection(ConfigurationManager.ConnectionStrings["ApplicationServices"].ToString());
    SqlCommand cmd = new SqlCommand();
    SqlDataAdapter da = new SqlDataAdapter();
    DataTable dt = new DataTable();
    DataRow dr;
 
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            //Add some column to datatable display some products information           
            dt.Columns.Add("prodName");
            dt.Columns.Add("prodDesc");
            dt.Columns.Add("prodPrice");
 
            //Add rows with datatable and bind in the grid view
            dr = dt.NewRow();
            dr["prodName"] = "MindStick Cleaner";
            dr["prodDesc"] = "Cleans all system dummy data";
            dr["prodPrice"] = "$100.00";
            dt.Rows.Add(dr);
 
            dr = dt.NewRow();
            dr["prodName"] = "MindStick DataConverter";
            dr["prodDesc"] = "Helps to import export data in different format";
            dr["prodPrice"] = "$120.00";
            dt.Rows.Add(dr);
 
            dr = dt.NewRow();
            dr["prodName"] = "MindStick SurveyManager";
            dr["prodDesc"] = "Helps creating survey page with specified format dll";
            dr["prodPrice"] = "$140.00";
            dt.Rows.Add(dr);
 
            dr = dt.NewRow();
            dr["prodName"] = "MindStick TeraByte Importer";
            dr["prodDesc"] = "Data transfer utility";
            dr["prodPrice"] = "$30.00";
            dt.Rows.Add(dr);
 
            gvPayPal.DataSource = dt;
            gvPayPal.DataBind();
        }
    }
 
    protected void gvPayPal_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "buy")
        {
            ImageButton ib = (ImageButton)e.CommandSource;
            int index = Convert.ToInt32(ib.CommandArgument);
            GridViewRow row = gvPayPal.Rows[index];
 
            //Get each Column label value from grid view and store it in label
            Label pName = (Label)row.FindControl("lblName");
            Label pDescription = (Label)row.FindControl("lblDescription");
            Label pPrice = (Label)row.FindControl("lblProductPrice");
 
            //Here store that person name who are going to make transaction
            Session["user"] = "Arun Singh";
 
            // make query string to store logged in user information in sql server table         
            string query = "";
            query = "insert into purchase(pname,pdesc,price,uname) values('" + pName.Text + "','" + pDescription.Text + "','" + pPrice.Text.Replace("$", "") + "','" + Session["user"].ToString() + "')";
            Con.Open();
            cmd = new SqlCommand(query, Con);
            cmd.ExecuteNonQuery();
            Con.Close();
 
            //Pay pal process Refer for what are the variable are need to send http://www.paypalobjects.com/IntegrationCenter/ic_std-variable-ref-buy-now.html
 
            string redirectUrl = "";
 
            //Mention URL to redirect content to paypal site
            redirectUrl += "https://www.sandbox.paypal.com/cgi-bin/webscr?cmd=_xclick&business=" + ConfigurationManager.AppSettings["paypalemail"].ToString();
 
            //First name I assign static based on login details assign this value
            redirectUrl += "&first_name=Arun_Seller";
           
            //Product Name
            redirectUrl += "&item_name=" + pName.Text;
 
            //Product Amount
            redirectUrl += "&amount=" + pPrice.Text;
 
            //Business contact paypal EmailID
            redirectUrl += "&business=arunse_1358772383_biz@gmail.com";
 
            //Shipping charges if any, or available or using shopping cart system
            redirectUrl += "&shipping=5";
 
            //Handling charges if any, or available or using shopping cart system
            redirectUrl += "&handling=5";
 
            //Tax charges if any, or available or using shopping cart system
            redirectUrl += "&tax=5";
 
            //Quantiy of product, Here statically added quantity 1
            redirectUrl += "&quantity=1";
 
            //If transactioin has been successfully performed, redirect SuccessURL page- this page will be designed by developer
            redirectUrl += "&return=" + ConfigurationManager.AppSettings["SuccessURL"].ToString();
 
            //If transactioin has been failed, redirect FailedURL page- this page will be designed by developer
            redirectUrl += "&cancel_return=" + ConfigurationManager.AppSettings["FailedURL"].ToString();
 
            Response.Redirect(redirectUrl);
        }
    }
}

Page Design:

To save the product information simply, I’m using a SQL table with following format or design.

USE [MyDatabase]
GO
 
/****** Object:  Table [dbo].[purchase]    Script Date: 01/27/2013 09:26:07 ******/
SET ANSI_NULLS ON
GO
 
SET QUOTED_IDENTIFIER ON
GO
 
SET ANSI_PADDING ON
GO
 
CREATE TABLE [dbo].[purchase](
      [Id] [int] IDENTITY(1,1) NOT NULL,
      [PName] [nvarchar](100) NULL,
      [PDesc] [nvarchar](100) NULL,
      [Price] [money] NULL,
      [Uname] [varchar](50) NULL,
 CONSTRAINT [PK_purchase] PRIMARY KEY CLUSTERED
(
      [Id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
 
GO
 
SET ANSI_PADDING OFF
GO

 There are some changes are necessary to web.config file, so please make some following changes in your config file.

<?xml version="1.0"?>
<!--
  For more information on how to configure your ASP.NET application, please visit
  http://go.microsoft.com/fwlink/?LinkId=169433
  -->
<configuration>
  <connectionStrings>
    <add name="ApplicationServices"connectionString="data source=Arun-PC;Integrated Security=true; Initial Catalog= MyDatabase; User Id= Arun-PC; Password= mindstick;"providerName="System.Data.SqlClient"/>
  </connectionStrings>
  <system.web>
    <compilation debug="true" targetFramework="4.0"/>
    <authentication mode="Forms">
      <forms loginUrl="~/Account/Login.aspx"timeout="2880"/>
    </authentication>
    <membership>
      <providers>
        <clear/>
        <add name="AspNetSqlMembershipProvider"type="System.Web.Security.SqlMembershipProvider"connectionStringName="ApplicationServices"enablePasswordRetrieval="false"enablePasswordReset="true"requiresQuestionAndAnswer="false"requiresUniqueEmail="false" maxInvalidPasswordAttempts="5" minRequiredPasswordLength="6" minRequiredNonalphanumericCharacters="0" passwordAttemptWindow="10" applicationName="/"/>
      </providers>
    </membership>
    <profile>
      <providers>
        <clear/>
        <add name="AspNetSqlProfileProvider"type="System.Web.Profile.SqlProfileProvider"connectionStringName="ApplicationServices"applicationName="/"/>
      </providers>
    </profile>
    <roleManager enabled="false">
      <providers>
        <clear/>
        <add name="AspNetSqlRoleProvider"type="System.Web.Security.SqlRoleProvider"connectionStringName="ApplicationServices"applicationName="/"/>
        <add name="AspNetWindowsTokenRoleProvider"type="System.Web.Security.WindowsTokenRoleProvider"applicationName="/"/>
      </providers>
    </roleManager>
  </system.web>
  <appSettings>
    <add key="token" value="An5ns1Kso7MWUdW4ErQKJJJ4qi4-As2ovQR55m2h23ipWTc1rpRXWbGb "/>
    <add key="paypalemail" value="arunse_1358772383_biz@gmail.com"/>
    <!--Here i used sandbox site url only if you hosted in live change sandbox to live paypal URL-->
    <add key="PayPalSubmitUrl" value="https://www.sandbox.paypal.com/cgi-bin/webscr"/>
    <add key="FailedURL" value="http://localhost:49666/PayPalIntegration/Failed.aspx"/> <!--Failed Page URL-->
    <add key="SuccessURL" value="http://localhost:49666/Default.aspx"/> <!--Success Page URL-->
  </appSettings>
  <system.webServer>
    <modules runAllManagedModulesForAllRequests="true"/>
  </system.webServer>
</configuration>

Note: Make sure you are logged in the https://developer.paypal.com/ with your email id in the same browser during testing. It only working fine if you logged in such as deduct amount, add amount etc. Only Sandbox site we must logged in developer site during testing but not in live https://www.paypal.com after hosted it.

Now it show time, executes web application and clicked on BuyNow button and follow the instruction.

Now I’m clicking on MindStick Cleaner product to purchase.

To make a payment you can use paypal account or any other credit or debit international card. Here I’m using personal account to purchase this product.

After clicking button Login you’ve got some credential notification.

Now accept the term and condition and clicking on button ‘Agree and Continue’.

Now pay the amount and wait.

Your amount has been payed or debited. There will be three options visible after successfully payment, that options are Return to ArunSeller Test Store, Go to Paypal account overview and add funds from your bank. When you clicked on ArunSeller Test Store then it will return you on success URL page which are you specified in web.config file. Let’s have look of these GUI.

Arun Seller Test Store:

Go to Paypal account overview:

Add funds from your bank:

I hope this article is helping you to know about integrate PayPal in your website.