我试图将其减少到尽可能小的复制,但它仍然有点长,我很抱歉。
我有一个 F# 项目,它引用了一个 C# 项目,代码如下。
public static class CSharpClass {
public static async Task AsyncMethod(CancellationToken cancellationToken) {
await Task.Delay(3000);
cancellationToken.ThrowIfCancellationRequested();
}
}
这是 F# 代码。
type Message =
| Work of CancellationToken
| Quit of AsyncReplyChannel<unit>
let mkAgent() = MailboxProcessor.Start <| fun inbox ->
let rec loop() = async {
let! msg = inbox.TryReceive(250)
match msg with
| Some (Work cancellationToken) ->
let! result =
CSharpClass.AsyncMethod(cancellationToken)
|> Async.AwaitTask
|> Async.Catch
// THIS POINT IS NEVER REACHED AFTER CANCELLATION
match result with
| Choice1Of2 _ -> printfn "Success"
| Choice2Of2 exn -> printfn "Error: %A" exn
return! loop()
| Some (Quit replyChannel) -> replyChannel.Reply()
| None -> return! loop()
}
loop()
[<EntryPoint>]
let main argv =
let agent = mkAgent()
use cts = new CancellationTokenSource()
agent.Post(Work cts.Token)
printfn "Press any to cancel."
System.Console.Read() |> ignore
cts.Cancel()
printfn "Cancelled."
agent.PostAndReply Quit
printfn "Done."
System.Console.Read()
问题是,取消后,控制永远不会返回到异步块。我不确定它是挂在里面AwaitTask
还是Catch
. 直觉告诉我它在尝试返回之前的同步上下文时被阻塞,但我不确定如何确认这一点。我正在寻找有关如何解决此问题的想法,或者也许在这里有更深入了解的人可以发现问题。
可能的解决方案
let! result =
Async.FromContinuations(fun (cont, econt, _) ->
let ccont e = econt e
let work = CSharpClass.AsyncMethod(cancellationToken) |> Async.AwaitTask
Async.StartWithContinuations(work, cont, econt, ccont))
|> Async.Catch