.net - F# STA 线程异步

Question

我从 GUI 线程调用这个函数:

let updateImageLoop (pprocess : PlotProcess) (target : IUpdatableImageView<'T>) =
    async {
      while target.Continue do
        let context = System.Threading.SynchronizationContext.Current
        do! Async.SwitchToThreadPool()
        System.Threading.Thread.Sleep(10000)
        do! Async.SwitchToContext(context)
        let image = target.CreateImage()
        match image with
        | Some userImage -> do! target.UpdateImageView userImage 
        | None -> ()
    } |> Async.StartImmediate

方法 的时候问题就来了target.UpdateImageView 执行，产生异常:

The calling thread must be STA, because many UI components require this.

我知道，但这就是我所做的

do! Async.SwitchToContext(context)

消除函数 SwitchToContext 和 SwitchToThreadPool 会消除异常，但 GUI 只是卡住。这是有道理的，但为什么我不能在线程之间进行切换？？

产生问题的函数是 UpdateImageView。我在有和没有使它异步的情况下对其进行了测试。

member this.UpdateImageView  etoimage =
  async {
    let imageview = new Eto.Forms.ImageView()
    imageview.Image <- etoimage
    this.Content <- imageview
  }

编辑 - -

Testing with this code:
let updateImageLoop (pprocess : PlotProcess) (target : IUpdatableImageView<'T>) =
    let context = System.Threading.SynchronizationContext.Current
    let printThread text =
        printfn "[%d] %s" System.Threading.Thread.CurrentThread.ManagedThreadId text
    async {
      while target.Continue do
        printThread "begining"
        do! Async.SwitchToThreadPool()
        printThread "after swith to thread pool"
        let image = target.CreateImage()
        match image with
        | Some userImage -> 
            printThread "before switch to context"
            do! Async.SwitchToContext context 
            printThread "after switch to context"
            target.UpdateImageView userImage 
        | None -> ()
    } |> Async.StartImmediate

打印 :

[1] begining 
[4] after swith to thread pool 
[4] before switch to context 
[5] after switch to context

Answer 1

使用 [< STAThread >]

使用 guiContext 处理 GUI

在您的 GUI 创建(框架初始化)中，请记住 guiContext

let guiContext = System.Threading.SynchronizationContext.Current 

并将其传递给异步 GUI 执行

// the async GUI execute 
async {
            let currentContext = System.Threading.SynchronizationContext.Current 
            do! Async.SwitchToContext(guiContext)
            f() // work on the GUI
            do! Async.SwitchToContext(currentContext)   
}

将等待放在一个额外的步骤中，以保持它的可组合性。