Question

I am learning RX (Reactive Extensions), and have found someone posted some code nearly one year ago using F# and RX to make a simple webCrawler. I tried to see if I can re-use the code. I download RX, and create a F# windows application, add reference to System.Reactive. My IDE is VS 2010 Ultimate, RX version is: 1.1.11111. The following is the code:

#light
open System
open System.Linq
open System.Collections.Generic
open System.Net
open System.IO
open System.Threading
open System.Text.RegularExpressions
open System.Reactive
open System.Reactive.Linq

let create f =
    Observable.Create<_>(fun x ->
        f x
        new System.Action((fun () -> ())))

let ofAsync async =
    create (fun obs -> Async.StartWithContinuations(async, obs.OnNext,obs.OnError,obs.OnError))

let fromEvent (event:IEvent<_,_>) = create (fun x -> event.Add x.OnNext)

let tickEvent = new Event<unit> ()
let tickEventObs = tickEvent.Publish |> fromEvent

let fetch(url:string) =
    async { let req = WebRequest.Create(url)
            let! resp = req.AsyncGetResponse()
            let stream = resp.GetResponseStream()
            let reader = new StreamReader(stream)
            let! html = reader.AsyncReadToEnd()
            return html
          } |> ofAsync

But the code can not get compiled, I got the error message:
Error 1 The field, constructor or member ‘AsyncReadToEnd’ is not defined
So the error was on this line:

let! html = reader.AsyncReadToEnd()

I guess there could be some changes for the past one year in RX or F#.
For my current environment, what is the correct way to re-write the above code?
Thanks and happy new year to you all!
John

Answer 1

AsyncReadToEnd() extension method of StreamReader is part of FSharpPowerPack now. Install FSharpPowerPack from this link, if not yet, then add reference to FSharp.PowerPack to your project. This should make AsyncReadToEnd()method accessible from the rest of your code.