Asynchronous 捕获在不同线程上运行的异步工作流的异常

此代码未捕获异常。如何在单独的线程上启动异步工作流并在主程序中捕获异常？

由于没有等待的结果，因此无法捕获异常。您需要包装计算。一种可能性：

let failing = async {
    failwith "foo"
}

let test () =
    try
        Async.Start(failing)
    with
    | exn -> printf "caught"

---

作为替代方案，您可以将工作流作为任务启动，并使用其方法和属性。例如，

Task.Result

将再次重新引发异常，这样就可以工作了，这几乎就是您所尝试的：

let failing = async {
    failwith "foo"
}

let test () = 
    async {
        let! res = failing |> Async.Catch
        match res with
        | Choice1Of2 _ -> printf "success"
        | Choice2Of2 exn -> printfn "failed with %s" exn.Message
    } |> Async.Start

跑

---

在不同的线程上 抱歉-我刚刚看到您希望它位于不同的线程上-在这种情况下，您很可能希望使用RCH提供给您的内部方法-但是您也可以使用

ContinueWith

（尽管有点难看）：

---

无

Async.Catch

此外，您实际上不需要

Async.Catch

：

> test ();;
caught
val it : Task = System.Threading.Tasks.Task {AsyncState = null;
                                             CreationOptions = None;
                                             Exception = null;
                                             Id = 3;
                                             IsCanceled = false;
                                             IsCompleted = true;
                                             IsFaulted = false;
                                             Status = RanToCompletion;}

> test ();;
caught
val it : unit = ()

open System.Threading.Tasks

let test () = 
   (Async.StartAsTask failing).ContinueWith(fun (t : Task<_>) -> try t.Result with _ -> printfn "caught")

> test ();;
caught
val it : Task = System.Threading.Tasks.Task {AsyncState = null;
                                             CreationOptions = None;
                                             Exception = null;
                                             Id = 3;
                                             IsCanceled = false;
                                             IsCompleted = true;
                                             IsFaulted = false;
                                             Status = RanToCompletion;}

let test () = 
   async { 
      try 
         do! failing 
      with _ -> printfn "caught" 
   } |> Async.Start