错误F＃-c＃异步调用：转换Threading.Tasks.Task< MyType>到异步 [英] Error F# - c# async calls : converting Threading.Tasks.Task<MyType> to Async<'a>

问题描述

当我尝试从我的F＃代码中调用C＃库中的异步方法时。
我收到以下编译错误。

When I try to call an async method that is in C# library from my F# code. I get the following compilation error.

该表达式的类型应为Async<'a>，但此处的类型为Threading .Thread.Tasks.Task

This expression was expected to have type Async<'a> but here has type Threading.Thread.Tasks.Task

SendMessageAsync 在C＃库中，并返回 Threading.Thread.Tasks.Task< MyType>

SendMessageAsync is in C# library and returns Threading.Thread.Tasks.Task<MyType>

let sendEmailAsync message = 
    async {
        let! response = client.SendMessageAsync(message)
        return response
    }

推荐答案

要在 Task<'T> 和 Async<'T> 之间进行转换内置的 Async.AwaitTask 函数。

For converting between Task<'T> and Async<'T> there is a built-in Async.AwaitTask function.

在普通 Task 和 Async< unit> ，您可以创建一个辅助函数：

To convert between a plain Task and Async<unit> you can create a helper function:

type Async with
    member this.AwaitPlainTask (task : Task) =
        task.ContinueWith(fun t -> ())
        |> Async.AwaitTask

然后您可以这样称呼它：

Then you can call it like this:

let sendEmailAsync message = 
    async {
        let! response = Async.AwaitPlainTask <|client.SendMessageAsync(message)
        return response
    }

当然，在这种情况下，响应不能是（）之外的任何东西，因此您最好只写：

Of course, in this case, the response can't be anything other than (), so you might as well just write:

let sendEmailAsync message = Async.AwaitPlainTask <|client.SendMessageAsync(message)

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