Metode kustom perutean API Web

Saya memiliki pengontrol berikut:

public class CustomerController : ApiController
{
    private ICustomerService customerService;

    public CustomerController(ICustomerService customerService)
    {
        this.customerService= customerService;
    }

    public IEnumerable<Customer> GetAll()
    {
        return customerService.GetAll();
    }

    [HttpGet]
    public Customer GetCustomer(int id)
    {
        //Get customer code...
        return customer;
    }

    [ActionName("Save")]
    [AcceptVerbs("PUT")]
    [HttpPost]
    public int SaveCustomer(Customer customer)
    {
        //Save customer code...
        return customer.id;
    }

    [ActionName("Test")]
    [HttpGet]
    public string TestCustomer()
    {
        return "test";
    }

    [HttpDelete]
    public bool DeleteCustomer(int id)
    {
        //Delete customer code...
        return false;
    }
}

Saya memiliki RouteConfig default berikut:

public class RouteConfig
{
    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

        routes.MapRoute(
            name: "Default",
            url: "{controller}/{action}/{id}",
            defaults: new { controller = "Home", action = "Index", id = UrlParameter.Optional }
        );
    }
}

Dan WebApiConfig default berikut:

public static class WebApiConfig
{
    public static void Register(HttpConfiguration config)
    {
        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "api/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

        config.EnableSystemDiagnosticsTracing();
    }
}

Ketika saya mencoba ~api/Customer saya mendapatkan kesalahan berikut: Ditemukan beberapa tindakan yang cocok dengan permintaan: System.Collections.Generic.IEnumerable`1[Customer] GetAll() pada tipe MyApp.API.Controllers.PriceLevelController System.String TestCustomer () pada tipe MyApp.API.Controllers.CustomerController

Perubahan apa pada konfigurasi rute yang perlu saya lakukan agar metode default dan metode kustom saya berfungsi saat dipanggil dari klien?