404 error after adding Web API to an existing MVC Web Application

There's a great question here: How to add Web API to an existing ASP.NET MVC 4 Web Application project?

Unfortunately, it wasn't enough to solve my problem. I've tried twice to be sure I haven't done anything wrong. I right clicked on "Controllers" and added the item "Web API 2 Controller with actions, using Entity Framework" where I selected my model class and db context. Everything went fine... but still... everytime I've tried to access /api/Rest I was getting a 404 error (The name of my Controller is RestController).

It's working!!! I didn't want to believe, but guess what, the problem was related with the Global.asax routing order.

While it doesn't work with:

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    GlobalConfiguration.Configure(WebApiConfig.Register); //I AM THE 4th
    BundleConfig.RegisterBundles(BundleTable.Bundles);
}      

It works with:

protected void Application_Start()
{
    AreaRegistration.RegisterAllAreas();
    GlobalConfiguration.Configure(WebApiConfig.Register); //I AM THE 2nd
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
    BundleConfig.RegisterBundles(BundleTable.Bundles);
}      

Crazy, I know.

If you want to use WebAPI inside an existing MVC (5) project you have to do the following steps:
1.Add WebApi packages:

Microsoft.AspNet.WebApi
Microsoft.AspNet.WebApi.Client
Microsoft.AspNet.WebApi.Core
Microsoft.AspNet.WebApi.WebHost
Newtonsoft.Json

2.Add WebApiConfig.cs file to App_Start folder:

using System.Web.Http;

namespace WebApiTest
{
    public static class 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 }
            );
        }
    }
}

3.Add the following line to Glabal.asax:

GlobalConfiguration.Configure(WebApiConfig.Register);

Important note: you have to add above line exactly after AreaRegistration.RegisterAllAreas();

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