我想知道这是否是一个过于宽泛的问题，但最近我让自己遇到了一段代码，我想确定如何从 C# 转换为正确的 F#。旅程从here (1)开始(TPL-F# 交互的原始问题)，并继续 here (2) (我正在考虑将一些示例代码转换为 F#)。

示例代码太长，这里无法重现，但有趣的功能是 ActivateAsync , RefreshHubs和 AddHub .特别有趣的地方是

//Sorry for the inconvenience of shorterned code, for context see the link "here (1)"...
override this.ActivateAsync() =
    this.RegisterTimer(new Func<obj, Task>(this.FlushQueue), null, TimeSpan.FromMilliseconds(100.0), TimeSpan.FromMilliseconds(100.0)) |> ignore

    if RoleEnvironment.IsAvailable then
        this.RefreshHubs(null) |> Async.awaitPlainTask |> Async.RunSynchronously
    else
        this.AddHub("http://localhost:48777/") |> Async.awaitPlainTask |> Async.RunSynchronously

    //Return value comes from here.
    base.ActivateAsync()

member private this.RefreshHubs(_) =
    //Code omitted, in case mor context is needed, take a look at the link "here (2)", sorry for the inconvinience...
    //The return value is Task.
    //In the C# version the AddHub provided tasks are collected and then the
    //on the last line there is return await Task.WhenAll(newHubAdditionTasks) 
    newHubs |> Array.map(fun i -> this.AddHub(i)) |> Task.WhenAll

member private this.AddHub(address) =
    //Code omitted, in case mor context is needed, take a look at the link "here (2)", sorry for the inconvinience...
    //In the C# version:
    //...
    //hubs.Add(address, new Tuple<HubConnection, IHubProxy>(hubConnection, hub))
    //} 
    //so this is "void" and could perhaps be Async<void> in F#... 
    //The return value is Task.
    hubConnection.Start() |> Async.awaitTaskVoid |> Async.RunSynchronously
    TaskDone.Done

module Async =
    let AwaitTaskVoid : (Task -> Async<unit>) =
        Async.AwaitIAsyncResult >> Async.Ignore

type TaskBuilder(?continuationOptions, ?scheduler, ?cancellationToken) =
    let contOptions = defaultArg continuationOptions TaskContinuationOptions.None
    let scheduler = defaultArg scheduler TaskScheduler.Default
    let cancellationToken = defaultArg cancellationToken CancellationToken.None

Orleans has it's own task scheduler which provides the single threaded execution model used within grains. It's important that when running tasks the Orleans scheduler is used, and not the .NET thread pool.

Should your grain code require a subtask to be created, you should use Task.Factory.StartNew:

await Task.Factory.StartNew(() =>{ /* logic */ });

This technique will use the current task scheduler, which will be the Orleans scheduler.

You should avoid using Task.Run, which always uses the .NET thread pool, and therefore will not run in the single-threaded execution model.

最佳答案

您可以使用 TaskBuilder在 FSharpx 中并传入 TaskScheduler.Current .这是我尝试翻译 RefreshHubs .请注意 Task<unit>用于代替 Task .

let RefreshHubs _ =
    let task = TaskBuilder(scheduler = TaskScheduler.Current)
    task {
        let addresses = 
            RoleEnvironment.Roles.["GPSTracker.Web"].Instances
            |> Seq.map (fun instance ->
                let endpoint = instance.InstanceEndpoints.["InternalSignalR"]
                sprintf "http://%O" endpoint.IPEndpoint
            )
            |> Seq.toList

        let newHubs = addresses |> List.filter (not << hubs.ContainsKey)
        let deadHubs = hubs.Keys |> Seq.filter (fun x -> 
            not (List.exists ((=) x) addresses))

        // remove dead hubs
        deadHubs |> Seq.iter (hubs.Remove >> ignore)

        // add new hubs
        let! _ = Task.WhenAll [| for hub in newHubs -> AddHub hub |]
        return ()
    }

关于c# - 根据调度程序将 async-await C# 代码转换为 F#，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/24813359/