使用F#中的TaskCompletionSource用于.NET库

Question

考虑以下因素

type MyClass () = 
    member x.ReadStreamAsync(stream:Stream) =
        async {
            let tcs = new TaskCompletionSource<int>()
            let buffer = Array.create 2048 0uy
            let! bytesReadCount = stream.ReadAsync(buffer, 0, buffer.Length) |> Async.AwaitTask
            if bytesReadCount > 0 then
                for i in 0..bytesReadCount do
                    if buffer.[i] = 10uy then
                        tcs.SetResult(i)

            // Omitted more code to handle the case if 10uy is not found..

            return tcs.Task
        }

代码从流中读取,直到遇到某个字符(由字节值表示),此时方法返回的任务完成.

函数签名DoSomethingAsync是unit -> Async<Task<int>>,但我希望unit -> Task<int>它可以在.NET中更普遍地使用.

可以使用异步表达式在F#中完成,还是可以更多地依赖Task.NET 的构造？

Answer 1

鉴于您实际上没有在示例中使用异步工作流,最简单的解决方案是完全放弃它:

member x.DoSomethingAsync() =
    let tcs = new TaskCompletionSource<int>()
    Task.Delay(100).Wait()
    tcs.SetResult(10)
    tcs.Task

这个实现DoSomethingAsync有类型unit -> Task<int>.

我不清楚你到底想要做什么,但你为什么不这样做呢？

member x.DoSomethingAsync() =
    async {
        do! Async.Sleep 100
        return 10 } |> Async.StartAsTask

此实现也具有类型unit -> Task<int>.

根据更新的问题,这是一种方法:

member x.DoSomethingAsync(stream:Stream) =
    async {
        let buffer = Array.create 2048 0uy
        let! bytesReadCount =
            stream.ReadAsync(buffer, 0, buffer.Length) |> Async.AwaitTask
        if bytesReadCount > 0
        then
            let res =
                [0..bytesReadCount]
                |> List.tryFind (fun i -> buffer.[i] = 10uy)
            return defaultArg res -1
        else return -1
    }
    |> Async.StartAsTask

该DoSomethingAsync函数具有类型Stream -> System.Task<int>.我不知道该怎么办else,所以我只是说-1,但我相信你可以用更正确的东西来代替它.