Asynchronous disposables are similar to IDisposable but with the difference that it encapsulates an async dispose method called DisposeAsync.

type AsyncDisposable (cancel) =
    interface IAsyncDisposable with
        member this.DisposeAsync () =
            async {
                do! cancel ()

In additon the following static members have been defined:

  • Create : (unit -> Async<unit>) -> IAsyncDisposable, creates an IAsyncDisposable from an async cancel function. Same instantiating the object, but the return value here is anonymous.
  • Empty : unit -> IAsyncDisposable, creates an empty disposable that will do nothing if it’s disposed.
  • Composite : seq<IAsyncDisposable> -> IAsyncDisposable, creates a disposable from a sequence of disposables. If disposed then all the contained disposables will also be disposed.

The SubscribeAsync method for async observables returns an async disposable, and to cancel the subscription you need to call the DisposeAsync method.

let xs = ofSeq <| seq { 1 .. 5 }
let obv = MyObserver<int>()
let! subscription = xs.SubscribeAsync obv

// Unsubscribe
do! subscription.DisposeAsync ()