Instant Payment Notification w/ .NET WebApi 2.x

[tpfkakey]

This wasn't exactly provided in the samples for processing IPN, so I thought I'd share the pattern I followed to process IPN with a .NET WebApi 2.x endpoint (in my case, this is all in Azure).

first, you'll need references to System.Web.Http and System.Net.Http.  It breaks down to 3 pretty simple code blocks. 

>> The controller action -- ReceiveIPN()

>> Method to get the body from the content of the IPN POST -- ProcessIpn()

>> Method to send the response back to PayPal -- VerifyIpn()

in my case, i'm updating my sales system (Dynamics 365 for Sales Engagement) by simply creating a record in a transaction table and then updating that record a bit further down stream.  You'll put your own logging in those places. 

hope you find it helpful as a starting point!

[HttpPost]
[AllowAnonymous]
public IHttpActionResult ReceiveIPN()
{
//log ipn recieved
Guid newId = Guid.NewGuid();
string qs = ProcessIpn(Request, newId);

//fire and forget verification
Task.Run(() => VerifyIpn(qs, newId));

//reply
return Ok();
}

private string ProcessIpn(HttpRequestMessage requestMessage, Guid newId)
{
HttpContent requestContent = requestMessage.Content;
string strContent = requestContent.ReadAsStringAsync().Result;

//******stuff you don't care about - put your specific logging here******

Entity ppipn = new Entity("kewi_paypalipn");
ppipn["kewi_paypalipnid"] = newId;
ppipn["kewi_name"] = "testing paypal ipn";
ppipn["kewi_ipnmessagebody"] = strContent;
client.Create(ppipn);

//return the body

return strContent;
}

private void VerifyIpn(string qs, Guid recId)
{
var url = "https://ipnpb.paypal.com/cgi-bin/webscr?cmd=_notify-validate&" + qs;
var handler = new HttpClientHandler();
var httpClient = new HttpClient(handler);
var requestMessage = new HttpRequestMessage(HttpMethod.Post, url);
var responseMessage = httpClient.SendAsync(requestMessage).Result;

var result = responseMessage.Content.ReadAsStringAsync().Result;

//**** a little more stuff you don't care about... put your logging here********
string[] qsPairs = qs.Split('&');
var custom = "";
decimal trxAmount = 0;
var trxId = "";

foreach (string pair in qsPairs)
{
if (pair.IndexOf("custom", StringComparison.OrdinalIgnoreCase) >= 0)
{
custom = pair.Split('=')[1];
}

if (pair.IndexOf("mc_gross", StringComparison.OrdinalIgnoreCase) >= 0)
{
trxAmount = decimal.Parse(pair.Split('=')[1]);
}

if (pair.IndexOf("txn_id", StringComparison.OrdinalIgnoreCase) >= 0)
{
trxId = pair.Split('=')[1];
}
}

if (result.ToLower() == "verified")
{
var ppipn = new Entity("kewi_paypalipn");
ppipn["kewi_paypalipnid"] = recId;
ppipn["kewi_ipnresult"] = result.ToLower();
ppipn["kewi_accountlookup"] = new EntityReference{LogicalName = "account", Id = Guid.Parse(custom)};
ppipn["kewi_paymentamount"] = new Money {Value = trxAmount};
ppipn["kewi_merchantservice"] = "PayPal";
ppipn["kewi_paymenttrxid"] = trxId;
client.Update(ppipn);
}
}