Is there any sample for PayPal IPN

Question

I have an Asp.Net WEB API 2 project and I would like to implement an Instant Payment Notification (IPN) listener controller.

I can\'t find any example and nuget package

Answer 1

I was also looking for a solution similar to the OP's original question Is there any IPN listener controller example? At least a PaypalIPNBindingModel to bind the Paypal query. and I got to this page. I tried the other solutions mentioned in this thread, they all worked but I really need the PayPal query-to-model solution so I googling until I stumbled on Carlos Rodriguez's Creating a PayPal IPN Web API Endpoint blogpost.

Here's an overview on what Carlos did:

1. Create a model. Base the properties you'll define in the model from the ipn response you'll get from PayPal.

   public class IPNBindingModel
   {
       public string PaymentStatus { get; set; }
       public string RawRequest { get; set; }
       public string CustomField { get; set; }    
   }
   

2. Create a PayPal Validator class.

   public class PayPalValidator
   {
       public bool ValidateIPN(string body)
       {
           var paypalResponse = GetPayPalResponse(true, body);
           return paypalResponse.Equals("VERIFIED");
       }
   
       private string GetPayPalResponse(bool useSandbox, string rawRequest)
       {
           string responseState = "INVALID";
           string paypalUrl = useSandbox ? "https://www.sandbox.paypal.com/"
           : "https://www.paypal.com/";
   
           ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
           using (var client = new HttpClient())
           {
               client.BaseAddress = new Uri(paypalUrl);
               client.DefaultRequestHeaders.Accept.Clear();
               client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/x-www-form-urlencoded"));
               HttpResponseMessage response = client.PostAsJsonAsync("cgi-bin/webscr", "").Result;
               if (response.IsSuccessStatusCode)
               {
                   rawRequest += "&cmd=_notify-validate";
                   HttpContent content = new StringContent(rawRequest);
                   response = client.PostAsync("cgi-bin/webscr", content).Result;
                   if (response.IsSuccessStatusCode)
                   {
                       responseState = response.Content.ReadAsStringAsync().Result;
                   }
               }
           }
           return responseState;
       }
   }
   

3. Create your controller.

   [RoutePrefix("paypal")]
   public class PayPalController : ApiController
   {
       private PayPalValidator _validator;
   
       public PayPalController()
       {
          this._validator = new PayPalValidator();
       }
   
       [HttpPost]
       [Route("ipn")]
       public void ReceiveIPN(IPNBindingModel model)
       {
           if (!_validator.ValidateIPN(model.RawRequest)) 
               throw new Exception("Error validating payment");
   
           switch (model.PaymentStatus)
           {
   
               case "Completed":
                   //Business Logic
                   break;
           }
      }
   }
   

4. Create a model binder that will define how Web Api will automatically create the model for you.

   public class IPNModelBinder : IModelBinder
   {
       public bool BindModel(HttpActionContext actionContext, ModelBindingContext bindingContext)
       {
           if (bindingContext.ModelType != typeof(IPNBindingModel))
           {
              return false;
           }
       var postedRaw = actionContext.Request.Content.ReadAsStringAsync().Result;
   
       Dictionary postedData = ParsePaypalIPN(postedRaw);
       IPNBindingModel ipn = new IPNBindingModel
       {
           PaymentStatus = postedData["payment_status"],
           RawRequest = postedRaw,
           CustomField = postedData["custom"]
       };
   
       bindingContext.Model = ipn;
       return true;
   }
   
   private Dictionary ParsePaypalIPN(string postedRaw)
   {
       var result = new Dictionary();
       var keyValuePairs = postedRaw.Split('&');
       foreach (var kvp in keyValuePairs)
       {
           var keyvalue = kvp.Split('=');
           var key = keyvalue[0];
           var value = keyvalue[1];
           result.Add(key, value);
       }
   
       return result;
   }
   }
    }
   

5. Register your model binder to WebApiConfig.cs. config.BindParameter(typeof(IPNBindingModel), new IPNModelBinder());

Hope this helps somebody else. Thank you Carlos Rodriguez for your amazing code.