Asp.net web API CORS series/mysterious issue - asp.net

Question

I am facing a CORS policy problem and I do not know how to fix it. I tried many approaches but what makes me crazy is that the service works fine on some devices and I can utilize all its resources and works a little bit on others and does not work at others while the whole devices having the same configuration equally set. To be more clear I am having a Web application based entirely and only on AngularJS 2 and a Web API that exposes a few actions. I installed the IIS and hosted the Web API on the default Web Site, which means it can be called from port 80 for simplicity, and I hosted the Web application using port 4200. Now let's give more detail about my Web API application structure.
EMG.WebApi.Core -> this project is the core project in which I put the controller classes and the web configuration class
EMG.WebApi.WebHost -> this project is used merely for hosting and it contains a reference to the EMG.WebApi.Core project and is the one that contains the Global.asax and within its Application_Start I am calling the Register method of Configuration class of the WebApi.Core and give it as a parameter the GlobalConfiguration object to register my handlers, tracers etc.
using EMG.ElectrometerWS.WebApi.Core;
using System;
using System.Web.Http;
using EMG.ElectrometerWS.WebApi.Core.Configuration;
namespace EMG.ElectrometerWS.WebApi.WebHost
{
public class Global : System.Web.HttpApplication
{
protected void Application_Start(object sender, EventArgs e)
{
WebApiConfig.Register(GlobalConfiguration.Configuration);
GlobalConfiguration.Configuration.EnsureInitialized();
}
}
}
using EMG.ElectrometerWS.WebApi.Core.Handlers;
using EMG.ElectrometerWS.WebApi.Core.Tracer;
using System;
using System.Configuration;
using System.Web.Http;
using System.Web.Http.Cors;
using System.Web.Http.Tracing;
namespace EMG.ElectrometerWS.WebApi.Core.Configuration
{
public static class WebApiConfig
{
...
public static string CorsOrigin
{
get
{
string result =
ConfigurationManager.AppSettings.Get("CorsOrigin");
if (!string.IsNullOrEmpty(result))
{
return result;
}
throw new Exception("AppSetting CorsOrigin not found in
web.config file.");
}
}
public static void Register(HttpConfiguration config)
{
// Web API configuration and services
EnableCorsAttribute enableCors =
new EnableCorsAttribute(CorsOrigin, "*", "*");
config.EnableCors(enableCors);
// Web API routes
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
//config.Routes.MapHttpRoute(
// name: "Secret Api",
// routeTemplate: "secretapi/{controller}/{id}",
// defaults: new { id = RouteParameter.Optional },
// constraints: null,
// handler: new ApiKeyProtectionMessageHandler() {
// InnerHandler = new HttpControllerDispatcher(config)
// });
// Enable ASP.NET Web API tracing
//config.EnableSystemDiagnosticsTracing();
//config.Services.Replace(typeof(ITraceWriter), new
// EntryExitTracer());
//config.Services.Replace(typeof(ITraceWriter), new WebApiTracer());
//config.MessageHandlers.Add(new EmptyPostBodyMessageHandler());
// Message handler to check the performance in production
environment ONLY
config.MessageHandlers.Add(new TracingHandler());
//config.MessageHandlers.Add(new XHttpMethodOverrideHandler());
config.MessageHandlers.Add(new JwtHandler());
}
}
}
EMG.ElectrometerWS.WebApi.WebHost Web.Cofig
<appSettings>
....
<add key="CorsOrigin" value="http://localhost:4200"/>
</appSettings>
What makes me crazy is that everything works fine on my colleague laptop and he can use all the actions. On mine I cannot call some of PUT methods while I can for others on other colleague/testers they can only call GET methods!!! And increases my surprises is that after clearing the browser history/cookies one of those laptops that have only GET methods being called have all things works fine.
What I have tried:
First I added the below code as you can notice above to the configuration class
EnableCorsAttribute enableCors =
new EnableCorsAttribute(CorsOrigin, "*", "*");
config.EnableCors(enableCors);
Creating the following handler and registered it as the first handler before other handlers
public class CorsPreflightHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage
request,
CancellationToken cancellationToken)
{
if (request.Headers.Contains("Origin") && request.Method == HttpMethod.Options)
{
var response = new HttpResponseMessage(HttpStatusCode.OK);
response.Headers.Add("Access-Control-Allow-Origin", "*");
response.Headers.Add("Access-Control-Allow-Methods", "*");
return response;
}
return await base.SendAsync(request, cancellationToken);
}
}
Removing the previous code and configured the CORS using the Web.config file of the WebHost project
<system.webServer>
<httpProtocol>
<customHeaders>
<add name="Access-Control-Allow-Origin" value="http:localhost:4200" />
<add name="Access-Control-Allow-Methods" value="*" />
<add name="Access-Control-Allow-Headers" value="*" />
</customHeaders>
</httpProtocol>
</system.webServer>
Finally removing the web config tags and enabled if on each controller class
[EnableCors(origins: "http://localhost:4200", headers: "*", methods: "*")]
public class XXXController : ApiController
{
Public string Get(int id)
{
return "value";
}
}

Answer 1

The CORS issue seems solved in meantime. I used the first approach by setting an application setting key/value for the allowed Origin then use that key/value to retrieve and register that Origin through a CORS attribute.
<appSettings>
....
<add key="CorsOrigin" value="http://localhost:4200"/>
</appSettings>
public static string CorsOrigin
{
get
{
string result =
ConfigurationManager.AppSettings.Get("CorsOrigin");
if (!string.IsNullOrEmpty(result))
{
return result;
}
throw new Exception("AppSetting CorsOrigin not found in web.config file.");
}
}
public static void Register(HttpConfiguration config)
{
....
EnableCorsAttribute enableCors =
new EnableCorsAttribute(CorsOrigin, "*", "*");
config.EnableCors(enableCors);
}
However, I still do not know what cause the problem from the beginning it may be an IIS issue or missing feature etc.