400 Response for asp.net web api POST request only when cors is enabled

Question

I've been stumped on this one for a few days now. I am a beginner to CORS so navigating this has been very confusing.

What's going wrong: I created a asp.net web api which can successfully send POST requests to my SQL database. I have used POSTMAN to send the data successfully. Once I enable CORS I can no longer send the data. I receive a 400 Bad Request.

Some References of my code:

My Controller which handles the POST request:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Web.Http;
using ClientsDataAccess;

namespace MS_Clients_Post.Controllers
{
    public class ClientsController : ApiController
    {
        public HttpResponseMessage Post([FromBody] Client client)
        {
            try
            {
                using (NewlandiaEntities entities = new NewlandiaEntities())
                {
                    entities.Clients.Add(client);
                    entities.SaveChanges();

                    var message = Request.CreateResponse(HttpStatusCode.Created, client);
                    message.Headers.Location = new Uri(Request.RequestUri +
                        client.Id.ToString());

                    return message;
                }
            }
            catch (Exception ex)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ex);
            }
        }

    }
}

My webAPIconfig.cs file (where I enabled CORS):

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web.Http;
using System.Web.Http.Cors;

namespace MS_Clients_Post
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services

            //enabling cors.  The "*","*","*" attributes allow all to access.  This should be more limited acccess in the future.
            var cors = new EnableCorsAttribute("*", "*", "*");
            config.EnableCors(cors);
            //end of cors code.

            // Web API routes
            config.MapHttpAttributeRoutes();

            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
        }
    }
}

What I'm seeing in Fiddler: OPTIONS Response 200 (Only returned with Angular APP, not POSTMAN

along with POST Response 400 BAD REQUEST (With POSTMAN or Angular APP

TLDR; POST request using ASP.net Web API works before enabling CORS. Why doesn't it work after?

Any help is greatly appreciated!

score 0 · Answer 1 · answered Feb 09 '18 at 20:01

I found the solution to my problem. This was a failure to identify what was actually going wrong. Couple different things:

When my application was deployed by VSTS to my development webserver it removed the SQL server login credentials from IIS application. (Advanced settings on IIS application pool).
Secondly and more importantly, the Syntax of my Angular Application was indeed not correct. Therefore the syntax was wrong from the Angular Application, but correct from POSTMAN (in postman I would use a GET method to get the JSON from server, and copy-paste the JSON to do a POST request).

Lesson learned, if it says 400 Bad Syntax, double check the syntax of what you are sending!

400 Response for asp.net web api POST request only when cors is enabled

1 Answers1