500 Error - Unable to select and perform a post action - winforms

Question

I am not good with Web API. Here is my problem. I send an Json serialized object from my Windows Form Application. The object is an Entity table. When I do a get response it returns a 500 server error. Basically I plan to have multiple post methods in one controller which I may not be doing right. So I need you guys to guide me on what I have been doing wrong.
Here is my Controller:
[ResponseType(typeof(HttpWebResponse)), HttpPost, ActionName("MerchandiseApi")]
public HttpResponseMessage PostMain(IList<IMF_Main> mainFromConsolidator)
{
if (!ModelState.IsValid)
return Request.CreateResponse(HttpStatusCode.BadRequest, 2);
using (var anthill = new AnthillConsolidatorEntities())
{
var main = new IMF_Main();
foreach (var item in mainFromConsolidator)
{
main.BrandID = item.BrandID;
main.ItemID = item.ItemID;
main.CategoryID = item.CategoryID;
main.SubCategoryID = item.SubCategoryID;
main.ClassID = item.ClassID;
main.GenderID = item.GenderID;
main.CoaID = item.CoaID;
main.SubCoaID = item.SubCoaID;
main.First_SRP = item.First_SRP;
main.Current_SRP = item.Current_SRP;
main.Previous_SRP = item.Previous_SRP;
main.isSenior = item.isSenior;
main.isActive = item.isActive;
main.DateCreated = item.DateCreated;
anthill.IMF_Main.Add(main);
anthill.SaveChanges();
}
}
return Request.CreateResponse(HttpStatusCode.OK, 1);
}
Here's my WebApiConfig:
public static void Register(HttpConfiguration config)
{
// Web API configuration and services
// Web API routes
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
config.Routes.MapHttpRoute(
name: "MerchandiseApi",
routeTemplate: "api/{controller}/{action}"
);
}
Here is where the Uri gets built: I have 2 more tables to send but I will start with this. This goes to my first Post method to the server
var jsonMain = JsonConvert.SerializeObject(consolidatorEntities.IMF_Main, Formatting.None);
HttpPost("http://localhost:50826/api/Merchandise/PostMain", jsonMain) == 1.ToString()
public string HttpPost(string uri, string json)
{
string content = "";
try
{
var request = (HttpWebRequest)WebRequest.Create(uri);
request.Method = "POST";
request.Accept = "application/json";
request.ContentType = "application/json";
byte[] bodyBytes = Encoding.UTF8.GetBytes(json);
request.GetRequestStream().Write(bodyBytes, 0, bodyBytes.Length);
request.GetRequestStream().Close();
var response = (HttpWebResponse)request.GetResponse();
var sr = new StreamReader(response.GetResponseStream(), Encoding.GetEncod
ing("UTF-8"));
content = sr.ReadToEnd();
sr.Close();
}
catch (Exception ex)
{
MessageBox.Show("Error sending data to Anthill \nException: " + ex, "Monytron - Consolidator", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
return content;
}

Answer 1

Problem
The main problem is with your routing. Routes will check in order so when you post a request to http://localhost:50826/api/Merchandise/PostMain and you have these routes in order:
"api/{controller}/{id}"
"api/{controller}/{action}"
So the first route will match:
If your PostMain method is the only action with [HttpPost], then mainFromConsolidator will be null in your foreach loop you will receive a NullReferenceException that result in a 500 error.
If you have multiple method decorated with [HttpPost], then the call is ambiguous between those actions and you will receive an InvalidOperationExpception with "Multiple actions were found that match the request" message that result in a 500 error.
The other problem is you are using an ActionName("MerchandiseApi") but didn't post to that action.
Solution
You can use multiple solutions. As an option you can define only one route:
"api/{controller}/{action}/{id}"
This way you can create a controller that contains actions like these:
public class SomeController
{
// matches GET /api/some/action1
[HttpGet]
public HttpResponseMessage Action1()
// matches GET /api/some/action2/5
[HttpGet]
public HttpResponseMessage Action2(int id)
// matches POST /api/some/action3
[HttpPost]
public HttpResponseMessage Action3(SomeType someParameter)
// matches POST /api/some/action4
[HttpPost]
public HttpResponseMessage Action4(SomeType someParameter)
}
Anyway if you decide to define multiple routes, pay attention that routes will match in order and also if you used ActionName attribute, then use that name in url to call that action.