404 error on ASP.NET Web API Controller

Question

I have created a ASP.NET MVC5 web application and then added HelpPages and Web Api components. The MVC web app and HelpPages worked fine, but I couldn't reach to the API Controller via http://localhost:port/api/Samples/GetAll. What can be wrong and how can I troubleshoot this?

WebApiConfig.cs

namespace MySolution.ApiV1
{
    using System.Web.Http;
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            // Web API configuration and services
            config.EnableCors();

            // Web API routes
            config.MapHttpAttributeRoutes();

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

API Controller

namespace MySolution.ApiV1.Controllers.Api
{
    [System.Web.Http.RoutePrefix("api/Samples")]
    public class SamplesController : System.Web.Http.ApiController
    {
        [System.Web.Http.HttpGet]
        [System.Web.Http.Route("GetAll")]            
        public System.Web.Http.IHttpActionResult Get()
        {
            return Ok("Hello Web API!");
        }
    }    
}

Global.ascx.cs

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    System.Web.Http.GlobalConfiguration.Configure(WebApiConfig.Register);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
}

Answer 1

I found the problem. The web api route must be called before the mvc route. I don't know why it makes a differences, but after I swap the orders, it worked.

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    System.Web.Http.GlobalConfiguration.Configure(WebApiConfig.Register); // call first
    RouteConfig.RegisterRoutes(RouteTable.Routes); // call second
    BundleConfig.RegisterBundles(BundleTable.Bundles);
}