Self寄宿

        static void Main(string[] args)
        {
            //Assembly.Load("WebApplication1, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null");    //加载外部程序集
            var config = new HttpSelfHostConfiguration("http://localhost:8080");

            config.Routes.MapHttpRoute(
                "API Default", "api/{controller}/{id}",
                new { id = RouteParameter.Optional });

            using (var server = new HttpSelfHostServer(config))
            {
                server.OpenAsync().Wait();
                Console.WriteLine("Press Enter to quit.");
                Process.Start("http://localhost:8080/api/xx");
                Console.ReadLine();
            }
        }

 public class xxController: Controller
    {
        public IEnumerable<string> Get()
        {
            return new string[] { "", "" };
        }
    }

OwinSelfHost

//  OWIN host
        //**********************************************************************************
        static void Main(string[] args)
        {
            string baseAddress = "http://localhost:9000/";
            // Start OWIN host
            using (WebApp.Start<Startup>(url: baseAddress))
            {
                // Create HttpCient and make a request to api/values
                HttpClient client = new HttpClient();

var response = client.GetAsync(baseAddress + "api/xx").Result;

Console.WriteLine(response);
                Console.WriteLine(response.Content.ReadAsStringAsync().Result);
                Console.ReadLine();
            }
        }

public class Startup
        {
            // This code configures Web API. The Startup class is specified as a type
            // parameter in the WebApp.Start method.
            public void Configuration(IAppBuilder appBuilder)
            {
                // Configure Web API for self-host.
                HttpConfiguration config = new HttpConfiguration();
                config.Routes.MapHttpRoute(
                    name: "DefaultApi",
                    routeTemplate: "api/{controller}/{id}",
                    defaults: new { id = RouteParameter.Optional }
                );

appBuilder.UseWebApi(config);
            }
        }

//**********************************************************************************

cross-origin support

var baseAddress = ConfigurationManager.AppSettings["baseAddress"];
            var config = new HttpSelfHostConfiguration(baseAddress);
            config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));
            config.Routes.MapHttpRoute(
                name: "DefaultApi",
                routeTemplate: "api/{controller}/{action}/{id}",
                defaults: new { id = RouteParameter.Optional }
            );
            var cors = new EnableCorsAttribute("*", "*", "*");//**********
            config.EnableCors(cors);
            var server = new HttpSelfHostServer(config);
            server.OpenAsync().Wait();

class Startup
{
    //  Hack from http://stackoverflow.com/a/17227764/19020 to load controllers in
    //  another assembly.  Another way to do this is to create a custom assembly resolver
    Type valuesControllerType = typeof(OWINTest.API.ValuesController);

    // This code configures Web API. The Startup class is specified as a type
    // parameter in the WebApp.Start method.
    public void Configuration(IAppBuilder appBuilder)
    {
        // Configure Web API for self-host.
        HttpConfiguration config = new HttpConfiguration();

        //  Enable attribute based routing
        //  http://www.asp.net/web-api/overview/web-api-routing-and-actions/attribute-routing-in-web-api-2
        config.MapHttpAttributeRoutes();

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

        appBuilder.UseWebApi(config);
    }
}

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Web.Http;

namespace OWINTest.Service.API
{
    [RoutePrefix("api/testing")]
    public class RoutedController : ApiController
    {
        [Route("getall")]
        public IEnumerable<string> GetAllItems()
        {
            return new string[] { "value1", "value2" };
        }
    }
}

public partial class APIServiceTest : ServiceBase
{
    public string baseAddress = "http://localhost:9000/";
    private IDisposable _server = null;

    public APIServiceTest()
    {
        InitializeComponent();
    }

    protected override void OnStart(string[] args)
    {
        _server = WebApp.Start<Startup>(url: baseAddress);
    }

    protected override void OnStop()
    {
        if(_server != null)
        {
            _server.Dispose();
        }
        base.OnStop();
    }
}

https://github.com/danesparza/OWIN-WebAPI-Service