ASP.NET Web API Owin SelfHost

WebApiOwinSelfHostInFSharp.fs

open Microsoft.Owin.Hosting
open Owin
open System
open System.Net
open System.Net.Http
open System.Web.Http

type HttpRouteDefaults = { Controller : string; Id : obj }

type HomeController() =
    inherit ApiController()
    member this.Get() =
        this.Request.CreateResponse(
            HttpStatusCode.OK,
            "Hello from F#")

type Startup() = 
    member this.Configuration(app : IAppBuilder) =
        let configuration = new HttpConfiguration()
        configuration.Routes.MapHttpRoute(
            "DefaultAPI",
            "api/{controller}/{id}",
            { Controller = "Home"; Id = RouteParameter.Optional }) |> ignore
        app.UseWebApi configuration |> ignore

[<EntryPoint>]
let main argv = 
    let server = WebApp.Start<Startup> ("http://localhost:9001")
    Console.WriteLine("Server running on http://localhost:9001")
    Console.WriteLine("Press enter to exit")
    Console.ReadLine() |> ignore
    server.Dispose()
    0

you can get rid of .Dispose() by using use keyword, see my fork.