Optional query parameters in WebAPI with F#

TestController.fs

module Web

open System.Web.Http

[<AllowNullLiteral>]
type QueryModel() =
    member val Top = 50 with get, set
    member val Skip = 0 with get, set

[<RoutePrefix("api/test")>]
type TestController() = 
    inherit ApiController()

    [<HttpGet; Route("")>]
    member controller.Get ([<FromUri>]model : QueryModel) =
        let model = if model = null then QueryModel() else model
        async {
            return seq { model.Skip .. (model.Top + model.Skip) }
        }
        |> Async.StartAsTask