1. Log in to the PayPal Developer Portal and download the Payflow .NET SDK.
2. Extract the files from the .zip file, and install the SDK.
3. Once the SDK is installed, rename the file from payflow_dotNET_2.0.dll to payflow_dotNET.dll.

1. Open Visual Studio.
2. Select File > New Project.

1. For this example, create a C#, ASP.NET Web Application called "MyFirstAPICall" as shown here:
2. Click OK, and you'll see your first page, Default.aspx.

1. Right-click References under Solution Explorer, then select Add Reference.
2. On the Browse tab, go to the Payflow_dotNET.dll file, then click OK.

1. Go back to the Default.aspx page.
2. Click Design.
3. Drag a Button from the toolbox onto the page.

1. Double-click the new button.
2. By default you'll see the following code:

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
namespace MyFirstAPICall{

public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e){
}

protected void Button1_Click(object sender, EventArgs e){
}
}
}

3. Add the following statements to the "using" section to include the PayPal SDK DLL for the file:

using PayPal.Payments.Common.Utility;
using PayPal.Payments.Communication;
using PayPal.Payments.DataObjects;

​

1. The following is sample code for the Button1_Click function:
      

   //Set your API Credentials	
   /////////////////////////////////////////////
   //PLEASE NOTE THIS IS NOT CONSIDERED SECURE//
   //THIS IS FOR EXAMPLE PURPOSES ONLY//////////
   /////////////////////////////////////////////
   
   string USER = "xxxx";
   string VENDOR = "xxxx";
   string PARTNER = "PayPal";
   string PWD = "xxxxx";
   
   //set the port
   int hostPort = 443;
   
   //set the timeout
   int timeOut = 30;
   
   //set the host address (pilot-) for testing
   string hostAddress = "pilot-payflowpro.paypal.com";
   
   //build a test request string
   string Request = "USER=" + USER + "&PWD=" + PWD + "&VENDOR=" + VENDOR + "&PARTNER=" + PARTNER
   + "&TRXTYPE=S&TENDER=C&ACCT=4111111111111111&EXPDATE=1213&CVV2=123&AMT=99.00&FIRSTNAME=John&LASTNAME=Smith&STREET=123
   Main St.&CITY=San Jose&STATE=CA&ZIP=12345&COMMENT1=Reservation&VERBOSITY=MEDIUM";
   
   //build a Payflow API Object with the address, port, and timeout
   PayflowNETAPI pfObj = new PayflowNETAPI(hostAddress, hostPort, timeOut);
   
   //set the response variable to the value of the response from the call and make the call
   string response = pfObj.SubmitTransaction(Request + PayflowUtility.RequestId, PayflowUtility.RequestId);
   
   //get the status from the response
   string status = PayflowUtility.GetStatus(response);
   
   //print the status to the page
   Response.Write(status);
   Response.Write("<br />");//line break
   
   //API Request:
   Response.Write("API Request:\n");
   Response.Write("<br />");//line break
   
   //print the raw request string to the page
   Response.Write(Request);
   Response.Write("<br />");//line break
   
   //API Response:
   Response.Write("\nAPI Response:\n");
   Response.Write("<br />");//line break
   
   //print the raw API response String to the page
   Response.Write(response);

2. Set the USER, VENDOR, PARTNER, and PWD variables to your API credentials for the Payflow API.
3. Set the preceding code between the curly braces for the Button1_Click function.

1. Under Build, select Build MyFirstAPICall.
2. Click the green arrow to run the application.
3. Your browser will open and you'll see the button, which will be labeled Button (unless you changed it).
4. Click the button to show your API Request and Response. For example, the following message indicates a successful transaction: